UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the Securities

Exchange Act of 1934

Filed by the Registrant  ☑                            Filed by a Party other than the Registrant  ☐

Check the appropriate box:

GULFMARK OFFSHORE, INC.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):

JOINT LETTER TO STOCKHOLDERS OF TIDEWATER INC. AND STOCKHOLDERS OF GULFMARK OFFSHORE, INC.

Dear Stockholders:

Tidewater Inc. (“Tidewater”) and GulfMark Offshore, Inc. (“GulfMark”) have entered into a merger agreement providing for the combination of Tidewater with GulfMark (the “business combination”), pursuant to which (a) Gorgon Acquisition Corp., a wholly-owned subsidiary of Tidewater to be formed as a corporation organized in the State of Delaware (“Merger Sub 1”) will merge with and into GulfMark, with GulfMark surviving such merger (the “first merger”), and (b) immediately thereafter, GulfMark will merge with and into Gorgon NewCo, LLC, another wholly-owned subsidiary of Tidewater to be formed as a limited liability company organized in the State of Delaware (“Merger Sub 2”), with such subsidiary as the surviving entity in such merger (the “second merger” and, together with the first merger, the “mergers”). Tidewater stockholders as of the close of business on October 10, 2018, the record date, are invited to attend a special meeting of Tidewater stockholders to be held on November 15, 2018, at 9:00 AM Central Time at the offices of Weil, Gotshal & Manges LLP at 700 Louisiana Street, Suite 1700, Houston, Texas 77002 to consider and vote upon a proposal to approve the issuance of Tidewater common stock (the “Tidewater issuance proposal”), in connection with the business combination. GulfMark stockholders as of the close of business on October 12, 2018, the record date, are invited to attend a special meeting of GulfMark stockholders on November 15, 2018, at 9:00 AM Eastern Time at the offices of Gibson, Dunn & Crutcher LLP at 200 Park Avenue, New York, NY 10166 to consider and vote upon a proposal to adopt the merger agreement (the “GulfMark merger proposal”) and certain other matters related to the business combination.

If you are a GulfMark stockholder and the business combination contemplated by the merger agreement is completed, you will be entitled to receive, for each issued and outstanding share of GulfMark common stock owned by you immediately prior to the effective time of the first merger, 1.100 of a fully paid, validly issued and nonassessable share of Tidewater common stock (the “exchange ratio”). For a description of the consideration that GulfMark stockholders will receive upon completion of the business combination, see the section entitled “The Business Combination—Consideration to GulfMark Stockholders” beginning on page 74 of the accompanying joint proxy statement/prospectus.

GulfMark restricted stock units representing a right to vest in and be issued shares of GulfMark common stock (collectively, “GulfMark RSUs”) which remain unvested or unissued as of the effective time of the first merger will be converted into an award to acquire Tidewater common stock on substantially the same terms and conditions as applied to such award prior to the effective time of the first merger, as adjusted to reflect the exchange ratio. GulfMark warrants that are outstanding will be converted automatically into warrants representing a right to acquire Tidewater common stock on substantially the same terms and conditions as applied to such warrants immediately prior to the effective time of the first merger, but subject to the limitations on foreign ownership set forth in the Tidewater certificate of incorporation intended to comply with the Jones Act (as defined in the accompanying joint proxy statement/prospectus), as adjusted to reflect the exchange ratio. For a description of the treatment of GulfMark RSUs and GulfMark warrants upon completion of the business combination, see the section entitled “The Merger Agreement—Treatment of GulfMark Warrants and RSUs” beginning on page 127 of the accompanying joint proxy statement/prospectus.

Immediately following the completion of the business combination, the former Tidewater stockholders and GulfMark stockholders will own 74% and 26% of the combined company, respectively. Tidewater intends to list the Tidewater common stock to be issued in the first merger on the New York Stock Exchange (“NYSE”). The market value of the merger consideration will fluctuate with the price of Tidewater common stock. Based on the closing price of Tidewater common stock on July 13, 2018, the last trading day before the public announcement of the signing of the merger agreement, the value of the merger consideration payable to holders of GulfMark common stock upon completion of the business combination was approximately $33.68 per share. Based on the closing price of Tidewater common stock on October 9, 2018, the last practicable date before the date of filing of the joint proxy statement/prospectus accompanying this letter, the value of the merger consideration payable to holders of GulfMark common stock upon completion of the business combination was approximately $34.89 per share. GulfMark stockholders should obtain current stock price quotations for Tidewater common stock and GulfMark common stock. Tidewater common stock is traded on the NYSE under the symbol “TDW,” and GulfMark common stock is traded on NYSE American (the “NYSE MKT”) under the symbol “GLF.”

Based on certain representations, covenants and assumptions, all of which must continue to be true and accurate in all material respects as of the effective time of the mergers, it is the opinion of each of Tidewater’s counsel, Weil, Gotshal & Manges LLP, and GulfMark’s counsel, Gibson, Dunn & Crutcher LLP, that, for U.S. federal income tax purposes, the mergers qualify as a “reorganization” within the meaning of Section 368(a) of the Internal Revenue Code of 1986, as amended, (the “Code”). Assuming the mergers qualify as a reorganization, a stockholder of GulfMark generally will not recognize any gain or loss upon receipt of the merger consideration in the first merger except to the extent such stockholder receives any cash received in lieu of a fractional share of Tidewater common stock, as discussed in the section entitled “Material U.S. Federal Income Tax Consequences of the Business Combination” beginning on page 159 of the accompanying joint proxy statement/prospectus.

Tidewater and GulfMark will each hold a special meeting of their respective stockholders to consider and vote upon certain matters relating to the proposed business combination. Tidewater and GulfMark cannot complete the proposed business combination unless, among other things, Tidewater stockholders approve the Tidewater issuance proposal in connection with the first merger, and GulfMark stockholders approve the GulfMark merger proposal.

Your vote is very important. To ensure your representation at your company’s special meeting, please complete and return the enclosed proxy card or submit your proxy via the Internet or by telephone. Please vote promptly whether or not you expect to attend your company’s special meeting. Submitting a proxy now will not prevent you from being able to vote in person at your company’s special meeting if you are otherwise eligible to vote at such meeting.

Raging Capital Management, LLC (“Raging”) and 5 Essex, L.P. (“Captain Q”) have each entered into a voting and support agreement with Tidewater pursuant to which each has agreed, among other things, to vote a portion of the shares of GulfMark common stock that it beneficially owns (constituting in the aggregate approximately 34.99% of the issued and outstanding shares of GulfMark common stock as of July 15, 2018) in favor of the approval of the GulfMark merger proposal, on the terms and subject to the conditions set forth in the applicable voting and support agreement.

The Tidewater board of directors (the “Tidewater Board”) has unanimously determined that the merger agreement, the mergers and the other transactions contemplated by the merger agreement are fair to, and in the best interests of, Tidewater and its stockholders, has unanimously approved and declared advisable the merger agreement, the mergers and the other transactions contemplated by the merger agreement including the Tidewater issuance proposal in connection with the mergers, and unanimously recommends that Tidewater stockholders vote “FOR” the Tidewater issuance proposal and, if necessary, “FOR” the Tidewater adjournment proposal (as defined in the accompanying joint proxy statement/prospectus).

The GulfMark board of directors (the “GulfMark Board”) has unanimously determined that the merger agreement, the mergers and the other transactions contemplated by the merger agreement are fair to, and in the best interests of, GulfMark and its stockholders, has unanimously approved and declared advisable the merger agreement, the mergers and the other transactions contemplated by the merger agreement and unanimously recommends that GulfMark stockholders vote “FOR” the GulfMark merger proposal and “FOR” each of the other GulfMark proposals described in the accompanying joint proxy statement/prospectus.

The obligations of Tidewater and GulfMark to consummate the business combination are subject to the satisfaction or waiver of the conditions set forth in the merger agreement, a copy of which is included as part of the accompanying joint proxy statement/prospectus. The joint proxy statement/prospectus provides you with detailed information about the proposed business combination. It also contains or, in the case of GulfMark, references information about Tidewater and GulfMark and certain related matters. You are encouraged to read the joint proxy statement/prospectus carefully and in its entirety. In particular, you should carefully read the section entitled “Risk Factors” beginning on page 29 of the accompanying joint proxy statement/prospectus for a

discussion of risks you should consider in evaluating the Tidewater issuance proposal and the GulfMark merger proposal and how they will affect you.

Sincerely,

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the business combination, the adoption of the merger agreement, the issuance of Tidewater common stock in connection with the business combination or any other transactions described in the accompanying joint proxy statement/prospectus, or passed upon the adequacy or accuracy of the disclosure in this document. Any representation to the contrary is a criminal offense.

This document is dated October 17, 2018, and is first being mailed to stockholders of Tidewater and GulfMark on or about October 17, 2018.

TIDEWATER INC. NOTICE OF SPECIAL MEETING OF STOCKHOLDERS TO BE HELD ON NOVEMBER 15, 2018 AT 9:00 AM CENTRAL TIME

NOTICE IS HEREBY GIVEN that a special meeting of stockholders of Tidewater Inc. (“Tidewater”) will be held on November 15, 2018, at 9:00 AM Central Time at the offices of Weil, Gotshal & Manges LLP at 700 Louisiana Street, Suite 1700, Houston, Texas 77002, for the following purposes:

Tidewater stockholder approval of the Tidewater issuance proposal is required to complete the business combination. Tidewater stockholders will also be asked to approve, if necessary, the Tidewater adjournment proposal. Tidewater will transact no other business at the Tidewater special meeting. The record date for the Tidewater special meeting has been set as October 10, 2018. Only Tidewater stockholders of record as of the close of business on such record date are entitled to notice of, and to vote at, the Tidewater special meeting or any adjournments and postponements thereof.

The Tidewater board of directors unanimously recommends that you vote “FOR” the Tidewater issuance proposal and “FOR” the Tidewater adjournment proposal.

See the section entitled “Special Meeting of Tidewater Stockholders” beginning on page 60 of the joint proxy statement/prospectus accompanying this notice for additional information about the Tidewater issuance proposal and the Tidewater adjournment proposal. You should read the joint proxy statement/prospectus accompanying this notice carefully in its entirety before you vote.

PLEASE VOTE AS PROMPTLY AS POSSIBLE, WHETHER OR NOT YOU PLAN TO ATTEND THE TIDEWATER SPECIAL MEETING. IF YOU LATER DESIRE TO REVOKE OR CHANGE YOUR PROXY FOR ANY REASON, YOU MAY DO SO IN THE MANNER DESCRIBED IN THE ACCOMPANYING JOINT PROXY STATEMENT/PROSPECTUS. FOR FURTHER INFORMATION CONCERNING THE PROPOSALS BEING VOTED UPON, USE OF THE PROXY AND OTHER RELATED MATTERS, YOU ARE URGED TO READ THE ACCOMPANYING JOINT PROXY STATEMENT/PROSPECTUS.

BY ORDER OF THE BOARD OF

DIRECTORS,

Bruce D. Lundstrom

Executive Vice President, General Counsel

and Secretary

GULFMARK OFFSHORE, INC. NOTICE OF SPECIAL MEETING OF STOCKHOLDERS TO BE HELD ON NOVEMBER 15, 2018 AT 9:00 AM EASTERN TIME

NOTICE IS HEREBY GIVEN that a special meeting of stockholders of GulfMark Offshore, Inc. (“GulfMark”) will be held on November 15, 2018, at 9:00 AM Eastern Time at the offices of Gibson, Dunn & Crutcher LLP at 200 Park Avenue, New York, New York 10166, for the following purposes:

GulfMark stockholder approval of the GulfMark merger proposal is required to complete the business combination. GulfMark stockholders will also be asked to approve the GulfMark compensation proposal and, if necessary, the GulfMark adjournment proposal. GulfMark will transact no other business at the GulfMark special meeting. The record date for the GulfMark special meeting has been set as October 12, 2018. Only GulfMark stockholders of record as of the close of business on such record date are entitled to notice of, and to vote at, the GulfMark special meeting or any adjournments and postponements thereof.

The GulfMark board of directors unanimously recommends that you vote “FOR” the GulfMark merger proposal, “FOR” the GulfMark compensation proposal, and “FOR” the GulfMark adjournment proposal.

See the section entitled “Special Meeting of GulfMark Stockholders” beginning on page 67 of the joint proxy statement/prospectus accompanying this notice for additional information about the GulfMark merger proposal, the GulfMark compensation proposal and the GulfMark adjournment proposal. You should read the joint proxy statement/prospectus accompanying this notice carefully in its entirety before you vote.

PLEASE VOTE AS PROMPTLY AS POSSIBLE, WHETHER OR NOT YOU PLAN TO ATTEND THE GULFMARK SPECIAL MEETING. IF YOU LATER DESIRE TO REVOKE OR CHANGE YOUR PROXY FOR ANY REASON, YOU MAY DO SO IN THE MANNER DESCRIBED IN THE ACCOMPANYING JOINT PROXY STATEMENT/PROSPECTUS. FOR FURTHER INFORMATION CONCERNING THE PROPOSALS BEING VOTED UPON, USE OF THE PROXY AND OTHER RELATED MATTERS, YOU ARE URGED TO READ THE ACCOMPANYING JOINT PROXY STATEMENT/PROSPECTUS.

BY ORDER OF THE BOARD OF

DIRECTORS,

Samuel R. Rubio

Senior Vice President, Chief Financial Officer

and Assistant Secretary

REFERENCES TO ADDITIONAL INFORMATION

This joint proxy statement/prospectus incorporates important business and financial information about GulfMark from other documents that GulfMark has filed with the Securities and Exchange Commission (the “SEC”), and that are not contained herein or delivered herewith. For a listing of documents incorporated by reference herein, please see the section entitled “Where You Can Find More Information” beginning on page 314. This information is available for you to review free of charge at the SEC’s public reference room located at 100 F Street, N.E., Washington, DC 20549, and through the SEC’s website at http://www.sec.gov.

You may request copies of this joint proxy statement/prospectus and any of the documents incorporated by reference herein or other information concerning Tidewater or GulfMark, without charge, upon written or oral request to the applicable company’s principal executive offices. The respective addresses and telephone numbers of such principal executive offices are listed below.

To obtain timely delivery of these documents before Tidewater’s special meeting of stockholders, Tidewater stockholders must request the information no later than November 7, 2018, which is five business days before the Tidewater special meeting.

To obtain timely delivery of these documents before GulfMark’s special meeting of stockholders, GulfMark stockholders must request the information no later than November 7, 2018, which is five business days before the GulfMark special meeting.

In addition, if you have questions about the business combination or the accompanying joint proxy statement/prospectus, would like additional copies of the joint proxy statement/prospectus or need to obtain proxy cards or other information related to the proxy solicitation, please contact MacKenzie Partners, Inc., the proxy solicitor for Tidewater, toll-free at 800-322-2885 or collect at 212-929-5500 or Innisfree, the proxy solicitor for GulfMark, collect at 212-750-5833 with respect to banks and brokers, or toll-free at 888-750-5834 with respect to stockholders and all others. You will not be charged for any of these documents that you request.

ABOUT THIS JOINT PROXY STATEMENT/PROSPECTUS

This document, which forms part of a registration statement on Form S-4 filed with the SEC by Tidewater (Registration No. 333-227111), constitutes a prospectus of Tidewater under Section 5 of the Securities Act of 1933, as amended (the “Securities Act”), with respect to the shares of common stock, par value $0.001 per share, of Tidewater (“Tidewater common stock”), to be issued to GulfMark stockholders pursuant to the merger agreement. This document also constitutes a proxy statement of each of Tidewater and GulfMark under Section 14(a) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”).

Tidewater has supplied all information contained herein relating to Tidewater, and GulfMark has supplied all information contained, or incorporated by reference, herein relating to GulfMark. Tidewater and GulfMark have both contributed to the information relating to the business combination contained in this joint proxy statement/prospectus.

You should rely only on the information contained or, in the case of GulfMark, incorporated by reference herein in connection with any vote, the giving or withholding of any proxy, or any investment decision in connection with the business combination. Tidewater and GulfMark have not authorized anyone to provide you with information that is different from that contained in or, in the case of GulfMark, incorporated by reference herein. This joint proxy statement/prospectus is dated October 17, 2018, and you should not assume that the information contained in this joint proxy statement/prospectus is accurate as of any date other than such date unless otherwise specifically provided herein. Further, you should not assume that the information with respect to GulfMark that is incorporated by reference herein is accurate as of any date other than the date of the incorporated document. Neither the mailing of this joint proxy statement/prospectus to Tidewater or GulfMark stockholders nor the proposals presented for approval of Tidewater stockholders or GulfMark stockholders pursuant to the merger agreement and this joint proxy statement/prospectus will create any implication to the contrary.

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QUESTIONS AND ANSWERS ABOUT THE BUSINESS COMBINATION AND THE SPECIAL MEETINGS

The following are answers to certain questions that you may have regarding the business combination, the Tidewater special meeting and the GulfMark special meeting. Tidewater and GulfMark urge you to read carefully the remainder of this joint proxy statement/prospectus because the information in this section may not provide all the information that you may consider important in determining how to vote. Additional important information is also contained in the annexes to, and, in the case of GulfMark, the documents incorporated by reference in this joint proxy statement/prospectus.

Tidewater. The Tidewater issuance proposal (as defined below) must be approved by the stockholders of Tidewater in accordance with the rules of the NYSE (the “NYSE rules”) as a condition to the completion of the business combination. Tidewater is convening a special meeting of its stockholders (the “Tidewater special meeting”) to seek approval of the Tidewater issuance proposal. Tidewater stockholders will also be asked to approve the adjournment of the Tidewater special meeting, if reasonably necessary to provide stockholders with any required supplement or amendment to this joint proxy statement/prospectus or solicit additional proxies in the event there are not sufficient votes at the time of the Tidewater special meeting to approve the Tidewater issuance proposal in connection with the business combination.

GulfMark. The merger agreement must be adopted by the stockholders of GulfMark in accordance with the General Corporation Law of the State of Delaware (the “DGCL”) in order for the business combination to be completed. GulfMark is holding a special meeting of its stockholders (the “GulfMark special meeting”) to seek approval of the merger agreement. GulfMark stockholders will also be asked to approve, on a non-binding, advisory basis, certain compensatory arrangements, as well as the adjournment of the GulfMark special meeting, if reasonably necessary to provide stockholders with any required supplement or amendment to this joint proxy statement/prospectus or solicit additional proxies in the event there are not sufficient votes at the time of the GulfMark special meeting to adopt the merger agreement.

GulfMark. The GulfMark special meeting will be held at 9:00 AM Eastern Time on November 15, 2018 at the offices of Gibson, Dunn & Crutcher LLP at 200 Park Avenue, New York, New York 10166.

GulfMark. The stockholders of GulfMark will be asked to:

GulfMark. Yes. The business combination cannot be completed unless the merger agreement is adopted by the holders representing a majority of the outstanding shares of GulfMark common stock entitled to vote thereon at the GulfMark special meeting. Only GulfMark stockholders as of the close of business on the record date are entitled to vote at the GulfMark special meeting. The board of directors of GulfMark (the “GulfMark Board”) unanimously recommends that GulfMark’s stockholders vote “FOR” the approval of the GulfMark merger proposal, “FOR” the approval of the GulfMark compensation proposal and “FOR” the approval of the GulfMark adjournment proposal.

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The Tidewater adjournment proposal. Approval of the Tidewater adjournment proposal, if necessary, requires the affirmative vote of a majority of the voting power present in person or by proxy at the Tidewater special meeting and entitled to vote on the proposal. Broker non-votes and shares held by Tidewater stockholders who neither are in attendance at, nor have submitted a proxy for, the Tidewater special meeting, will have no effect on the outcome of any vote on the Tidewater adjournment proposal. Votes to abstain will have the same effect as a vote “AGAINST” the Tidewater adjournment proposal.

The GulfMark compensation proposal. Approval of the GulfMark compensation proposal requires the affirmative vote of a majority of the shares of GulfMark common stock present in person or by proxy at the GulfMark special meeting and entitled to vote on the proposal. Broker non-votes and shares held by GulfMark stockholders who neither are in attendance at, nor have submitted a proxy for, the GulfMark special meeting will have no effect on the outcome of any vote to approve the GulfMark compensation proposal. Votes to abstain will have the same effect as a vote “AGAINST” the GulfMark compensation proposal.

The GulfMark adjournment proposal. Approval of the GulfMark adjournment proposal requires the affirmative vote of a majority of the shares of GulfMark common stock present in person or by proxy at the GulfMark special meeting and entitled to vote on the proposal. Broker non-votes and shares held by GulfMark stockholders who neither are in attendance at, nor have submitted a proxy for, the GulfMark special meeting will have no effect on the outcome of any vote to approve the GulfMark adjournment proposal. Votes to abstain will have the same effect as a vote “AGAINST” the GulfMark adjournment proposal.

For more information regarding the merger consideration to be provided to GulfMark stockholders, see the section entitled “The Business Combination—Consideration to GulfMark Stockholders” beginning on page 74. For more information regarding the conversion mechanics, see the section entitled “The Merger Agreement—Conversion of Shares; Exchange of Certificates” beginning on page 128.

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For more information regarding the treatment of GulfMark warrants, see the section entitled “The Merger Agreement—Treatment of GulfMark Warrants and RSUs—Treatment of GulfMark Warrants” beginning on page 127. For more information regarding the restrictions on exercise of the converted warrants, see the section entitled “Description of Tidewater Common Stock and Warrants” beginning on page 269.

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GulfMark. The GulfMark Board unanimously recommends that you vote “FOR” the approval of the GulfMark merger proposal, “FOR” the approval of the GulfMark compensation proposal, and “FOR” the approval of the GulfMark adjournment proposal. For more information regarding how the GulfMark Board recommends that you vote, see the section entitled “The Business Combination—Recommendation of the GulfMark Board and Reasons for the Business Combination” beginning on page 101.

GulfMark special meeting. The GulfMark Board has fixed October 12, 2018 as the record date for the GulfMark special meeting. All holders of record of shares of GulfMark common stock at the close of business on the record date are entitled to receive notice of, and to vote at, the GulfMark special meeting, provided that those shares remain outstanding on the date of the GulfMark special meeting. Your physical presence at the GulfMark special meeting is not required to vote. See the section entitled “Questions and Answers About the Business Combination and the Special Meetings—How can I vote my shares without attending the special meeting?” beginning on page 8 for instructions on how to vote your shares without attending the GulfMark special meeting.

Tidewater stockholders. If you are a stockholder of record of Tidewater common stock as of the close of business on the record date, and you vote by proxy via the Internet or by telephone or by signing, dating and returning your proxy card in the enclosed postage-paid envelope, you will have designated Bruce D. Lundstrom and Yang Xu as your proxies at the Tidewater special meeting, each with full power to act without the other and with full power of substitution.

GulfMark stockholders. If you are a stockholder of record of GulfMark common stock as of the close of business on the record date, and you vote by proxy via the Internet or by telephone or by signing, dating and returning your proxy card in the enclosed postage-paid envelope, you will have designated Quintin Kneen and Scott Winter as your proxies at the GulfMark special meeting, each with full power to act without the other and with full power of substitution.

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GulfMark stockholders. Each GulfMark stockholder of record is entitled to one vote for each share of GulfMark common stock held of record by him or her as of the close of business on the record date.

Quorum for Tidewater special meeting. A quorum will exist at the Tidewater special meeting with respect to each matter to be considered at the Tidewater special meeting if the holders of a majority of shares of Tidewater common stock issued and outstanding and entitled to vote as of the close of business on the record date are present in person or represented by proxy at the Tidewater special meeting. Shares of Tidewater common stock held in street name will be counted as present for the purpose of determining the existence of a quorum at the Tidewater special meeting so long as the beneficial owner thereof has given the bank, broker or other nominee voting instructions on at least one of the proposals brought before the Tidewater special meeting. The proposals for consideration at the Tidewater special meeting are considered “non-routine” matters, and therefore, no broker has discretion to vote on any of the proposals to be considered at the meeting without voting instructions from the beneficial owner of the shares. A stockholder’s shares will not be counted as present for the purpose of determining the existence of a quorum if no instructions have been provided on how to vote on any of the proposals.

Quorum for GulfMark special meeting. A quorum will exist at the GulfMark special meeting with respect to the matters to be considered at the GulfMark special meeting if the holders of a majority of shares of GulfMark common stock issued and outstanding and entitled to vote as of the close of business on the record date are present in person or represented by proxy at the GulfMark special meeting. Shares of GulfMark common stock held in street name will be counted as present for the purpose of determining the existence of a quorum at the GulfMark special meeting so long as the beneficial owner thereof has given the broker or other nominee voting instructions on at least one of the proposals brought before the GulfMark special meeting. The proposals for consideration at the GulfMark special meeting are considered “non-routine” matters, and, therefore, no broker has discretion to vote on any of the proposals to be considered at the meeting without voting instructions from the beneficial owner of the shares. A stockholder’s shares will not be counted as present for the purpose of determining the existence of a quorum if no instructions have been provided on how to vote on any of the proposals.

Immediately following the completion of the first merger, the surviving corporation will merge with and into Merger Sub 2 (the “second merger”). The first merger and the second merger are referred to together in this joint proxy statement/prospectus as the “mergers.” Upon completion of the second merger, the separate corporate existence of GulfMark will cease as a result and Merger Sub 2 will continue as the surviving company and a wholly owned subsidiary of Tidewater (which subsidiary is referred to as the “surviving company”).

GulfMark stockholders become entitled to receive the merger consideration at the effective time of the first merger, on the terms and subject to the conditions set forth in the merger agreement.

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Failure to bring the appropriate documentation may delay your entry into or prevent you from attending the Tidewater special meeting. The doors to the meeting room will be closed promptly at the start of the Tidewater special meeting, and stockholders will not be permitted to enter after that time.

GulfMark. Shares of GulfMark common stock held directly in your name as the stockholder of record as of the close of business on October 12, 2018, the record date, may be voted in person or by proxy at the GulfMark special meeting. If you choose to attend the GulfMark special meeting, you will need to bring proper identification, such as a driver’s license, in order to be admitted to the GulfMark special meeting. If you are a beneficial owner of GulfMark common stock but not the stockholder of record of such shares of GulfMark common stock, you will also need to bring proof of your beneficial ownership to be admitted to the GulfMark special meeting. A recent brokerage statement or a letter from a bank or broker are examples of acceptable proof of ownership. Please note that if your shares are held in “street name” by a bank, broker or other nominee and you wish to vote at the GulfMark special meeting, you will not be permitted to vote in

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person unless you first obtain a legal proxy issued in your name from the record owner and present it to the inspector of election with your ballot at the GulfMark special meeting. To request a legal proxy, please contact your bank, broker or other nominee holder of record. It is suggested you do so in a timely manner to ensure receipt of your legal proxy prior to the GulfMark special meeting.

Failure to bring the appropriate documentation may delay your entry into or prevent you from attending the GulfMark special meeting. The doors to the meeting room will be closed promptly at the start of the GulfMark special meeting, and stockholders will not be permitted to enter after that time.

GulfMark. If you are a stockholder of record of GulfMark common stock as of the close of business on October 12, 2018, the record date, you can vote by proxy via the Internet, by telephone or by mail by following the instructions provided on the enclosed proxy card. Please note that if you are a beneficial owner, you may vote by submitting voting instructions to your bank, broker or other nominee, or otherwise by following instructions provided by your bank, broker or other nominee. Internet and telephone voting may be available to a beneficial owner. Please refer to the voting instruction form provided by your bank, broker or other nominee.

GulfMark. If your shares of GulfMark common stock are registered directly in your name with GulfMark’s transfer agent, American Stock Transfer, you are considered the stockholder of record with respect to those shares, and access to proxy materials is being provided directly to you. If your shares are held by a bank, in a stock brokerage account or other nominee, then you are considered the beneficial owner of those shares, which are considered to be held in street name. Access to proxy materials is being provided to you by your bank, broker or other nominee who is considered the stockholder of record with respect to those shares.

Record holders (stockholders of record)

For shares of Tidewater and/or GulfMark common stock held directly in your name as the stockholder of record, please complete, sign, date and return each proxy card (or vote by proxy via the Internet or by

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telephone as provided on each proxy card) or otherwise follow the voting instructions provided in this joint proxy statement/prospectus in order to ensure that all of your shares of Tidewater and/or GulfMark common stock are voted.

Shares in “street name”

For shares of Tidewater and/or GulfMark common stock held in “street name” through a bank, broker or other nominee, you should follow the procedures provided by your bank, broker or other nominee to vote your shares.

GulfMark. If you are the record holder and you sign, date and return your proxy and do not indicate how you want your shares of GulfMark common stock to be voted, then your shares of GulfMark common stock will be voted “FOR” the approval of the GulfMark merger proposal, “FOR” the approval of the GulfMark compensation proposal, and “FOR” the approval of the GulfMark adjournment proposal.

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If you are a beneficial owner of Tidewater common stock as of the close of business on the record date, you must follow the instructions of your bank, broker or other nominee to revoke or change your voting instructions.

GulfMark. Yes. If you are a stockholder of record of GulfMark common stock as of the close of business on the record date, whether you vote via the Internet, by telephone or mail, you can change or revoke your proxy before it is voted at the GulfMark special meeting in one of the following ways:

If you are a beneficial owner of GulfMark common stock as of the close of business on the record date, you must follow the instructions of your bank, broker or other nominee to revoke or change your voting instructions.

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GulfMark. It is a condition to GulfMark’s obligation to consummate the business combination that GulfMark receive a written opinion of Gibson (or Weil, if Gibson does not render such opinion), dated as of the closing date, substantially to the effect that for U.S. federal income tax purposes, the mergers will qualify as a “reorganization” within the meaning of Section 368(a) of the Code.

Assuming the mergers qualify as a reorganization, a stockholder of GulfMark will not recognize any gain or loss upon receipt of Tidewater common stock in exchange for GulfMark common stock in the first merger and will recognize gain or loss with respect to any cash received in lieu of a fractional share of Tidewater common stock. The U.S. federal income tax consequences of the business combination are discussed in more detail in the section entitled “Material U.S. Federal Income Tax Consequences of the Business Combination” beginning on page 159. The discussion of the material U.S. federal income tax consequences contained in this joint proxy statement/prospectus is intended to provide only a general discussion and is not a complete analysis or description of all potential U.S. federal income tax consequences of the business combination’s foreign, state or local tax laws.

TAX MATTERS ARE COMPLICATED AND THE TAX CONSEQUENCES OF THE MERGERS WILL DEPEND ON THE FACTS OF YOUR OWN SITUATION. YOU SHOULD CONSULT YOUR OWN TAX ADVISOR AS TO THE SPECIFIC TAX CONSEQUENCES OF THE MERGERS TO YOU IN YOUR PARTICULAR CIRCUMSTANCES.

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GulfMark has retained Innisfree M&A Incorporated (“Innisfree”), to assist in the solicitation process. GulfMark will pay Innisfree a fee of approximately $30,000, as well as reasonable and documented out-of-pocket expenses. GulfMark has also agreed to indemnify Innisfree against various liabilities and expenses that relate to or arise out of its solicitation of proxies (subject to certain exceptions).

For a more complete summary of the conditions that must be satisfied or waived prior to completion of the business combination, see the section entitled “The Merger Agreement—Conditions to the Completion of the Business Combination” beginning on page 148.

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After receiving the proper documentation from you, following the effective time, the exchange agent will deliver to you the consideration (or if applicable, any cash in lieu of fractional shares) to which you are entitled. More information on the documentation you are required to deliver to the exchange agent can be found in the section entitled “The Merger Agreement—Conversion of Shares; Exchange of Certificates” beginning on page 128.

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RISK FACTORS

In addition to the other information contained or, in the case of GulfMark, incorporated by reference herein, including the matters addressed in the section entitled “Cautionary Statement Regarding Forward-Looking Statements” beginning on page 56, Tidewater stockholders should carefully consider the following risks before deciding how to vote with respect to the proposals to be considered and voted on at the Tidewater special meeting and GulfMark stockholders should carefully consider the following risks before deciding how to vote with respect to the proposals to be considered and voted on at the GulfMark special meeting. Tidewater stockholders and GulfMark stockholders should also consider the other information in this joint proxy statement/prospectus and, with respect to GulfMark, the other documents incorporated by reference herein, particularly the risk factors contained in GulfMark’s Annual Reports on Form 10-K and Quarterly Reports on Form 10-Q. See the section entitled “Where You Can Find More Information” beginning on page 314.

Risks Relating to the Business Combination

Because the market price of shares of Tidewater common stock will fluctuate prior to the consummation of the first merger, GulfMark stockholders cannot be certain of the precise value of the merger consideration they will receive in the first merger.

At the time the first merger is completed, each issued and outstanding share of GulfMark common stock (other than excluded shares as defined in the section entitled “The Business Combination—Consideration to GulfMark Stockholders” beginning on page 74) will be converted into the right to receive 1.100 shares of Tidewater common stock. The exchange ratio for the merger consideration is fixed, and there will be no adjustment to the merger consideration for changes in the market price of shares of Tidewater common stock or GulfMark common stock prior to the completion of the first merger. If the first merger is completed, there will be a time lapse between each of the date of this joint proxy statement/prospectus, the dates on which GulfMark stockholders vote to approve the GulfMark merger proposal at the GulfMark special meeting and Tidewater stockholders vote to approve the Tidewater issuance proposal at the Tidewater special meeting, and the date on which GulfMark stockholders entitled to receive the merger consideration actually receive such merger consideration. The market value of shares of Tidewater common stock may fluctuate during and after these periods as a result of a variety of factors (many of which are outside of Tidewater’s or GulfMark’s control), including general market and economic conditions, changes in Tidewater’s businesses, operations and prospects and regulatory considerations. Such factors are difficult to predict and in many cases may be beyond the control of Tidewater and GulfMark. Consequently, at the time GulfMark stockholders must decide whether to adopt the merger agreement, they will not know the actual market value of any merger consideration they will receive when the first merger is completed. The actual value of any merger consideration received by GulfMark stockholders at the completion of the first merger will depend on the market value of the shares of Tidewater common stock at that time. This market value may differ, possibly materially, from the market value of shares of Tidewater common stock at the time the merger agreement was entered into or at any other time. GulfMark stockholders should obtain current stock quotations for shares of Tidewater common stock before voting their shares of GulfMark common stock. For additional information about the GulfMark merger consideration, see the section entitled “The Merger Agreement—Merger Consideration” beginning on page 126.

The market price of shares of Tidewater common stock will continue to fluctuate after the completion of the business combination.

Upon completion of the business combination, holders of GulfMark common stock will become holders of shares of Tidewater common stock. The market price of shares of Tidewater common stock may fluctuate significantly following completion of the business combination and holders of GulfMark common stock could lose some or all of the value of their investment in Tidewater common stock. In addition, the stock market has experienced significant price and volume fluctuations which, if they continue to occur, could have a material adverse effect on the market for, or liquidity of, the Tidewater common stock, regardless of Tidewater’s actual operating performance.

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GulfMark stockholders will have a reduced ownership and voting interest in the combined company after the completion of the business combination and will exercise less influence over management.

Currently, GulfMark stockholders have the right to vote in the election of the GulfMark Board and the power to approve or reject any matters requiring stockholder approval under Delaware law and GulfMark’s certificate of incorporation and GulfMark’s bylaws. Upon completion of the business combination, each GulfMark stockholder who receives shares of Tidewater common stock in connection with the business combination will become a stockholder of Tidewater with a percentage ownership of Tidewater that is smaller than the GulfMark stockholder’s current percentage ownership of GulfMark. Upon completion of the business combination, each GulfMark warrant holder who exercises such holder’s warrant will become a stockholder of Tidewater with a percentage ownership of Tidewater that is smaller than the GulfMark warrant holder’s percentage ownership of GulfMark would have been had the warrant been exercised prior to closing. Based on the number of issued and outstanding shares of Tidewater common stock and shares of GulfMark common stock as of July 13, 2018 and on the exchange ratio of 1.100, with 7,500,275 shares of GulfMark common stock in the aggregate converted into the right to receive merger consideration, after completion of the first merger, GulfMark stockholders, in the aggregate, are expected to become owners of approximately 26% of the pro forma equity of the combined company, without giving effect to any shares of Tidewater common stock held by GulfMark stockholders prior to the completion of the business combination. Even if all former GulfMark stockholders voted together on all matters presented to Tidewater stockholders from time to time, the former GulfMark stockholders would exercise significantly less influence over Tidewater after the completion of the business combination relative to their influence over GulfMark prior to the completion of the business combination, and thus would have a less significant impact on the election of the Tidewater Board and on the approval or rejection of future Tidewater proposals submitted to a stockholder vote.

Shares of Tidewater common stock received by GulfMark stockholders as a result of the business combination will have different rights from shares of GulfMark common stock.

Upon completion of the business combination, GulfMark stockholders will no longer be stockholders of GulfMark, and GulfMark stockholders will become stockholders of Tidewater. There are certain differences between the current rights of GulfMark stockholders and the rights to which such stockholders will be entitled as stockholders of Tidewater. See the section entitled “Comparison of Stockholders’ Rights” beginning on page 276 for a discussion of the different rights associated with the shares of Tidewater common stock.

The market price of shares of Tidewater common stock may be affected by factors different from those that historically have affected shares of GulfMark common stock.

Upon completion of the business combination, holders of GulfMark common stock will become holders of Tidewater common stock. The operational focus and market presence of Tidewater differ from those of GulfMark in certain respects, and, accordingly, the financial position or results of operations and/or cash flows of Tidewater after the completion of the business combination, as well as the market price of shares of Tidewater common stock, may be affected by factors different from those currently affecting the financial position or results of operations and/or cash flows of GulfMark. Following the completion of the business combination, GulfMark will be part of a larger company with a broader geographic footprint, so decisions affecting GulfMark may be made in the context of the larger combined business as a whole rather than the GulfMark businesses individually. For a discussion of the businesses of Tidewater and GulfMark and of some important factors to consider in connection with those businesses, see the sections entitled “Information About the Companies” beginning on page 58 and “Additional Information About Tidewater” beginning on page 188, and, in the case of GulfMark, the documents incorporated by reference in the section entitled “Where You Can Find More Information” beginning on page 314, including, in particular, in the section entitled “Risk Factors” in GulfMark’s Annual Report on Form 10-K for the year ended December 31, 2017 and GulfMark’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2018.

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The merger agreement limits Tidewater’s ability and GulfMark’s ability to pursue alternatives to the business combination.

The merger agreement contains provisions that may discourage a third party from submitting an acquisition proposal to Tidewater or GulfMark that might result in greater value to Tidewater’s or GulfMark’s respective stockholders than the business combination, or may result in a potential acquirer of Tidewater, or a potential competing acquirer of GulfMark, proposing to pay a lower per share price to acquire Tidewater or GulfMark, respectively, than it might otherwise have proposed to pay. These provisions include a general prohibition on Tidewater and GulfMark from soliciting or, subject to certain exceptions relating to the exercise of fiduciary duties by the Tidewater Board or the GulfMark Board, entering into discussions with any third party regarding any acquisition proposal or offer for a competing transaction. GulfMark also has an unqualified obligation to submit the GulfMark merger proposal to a vote by its stockholders, even if GulfMark receives an alternative acquisition proposal that the GulfMark Board believes is superior to the business combination, and Tidewater has an unqualified obligation to submit the Tidewater issuance proposal to a vote by its stockholders, even if Tidewater receives an alternative acquisition proposal that the Tidewater Board believes is superior to the business combination, in each case unless Tidewater or GulfMark, as applicable, terminates the merger agreement in accordance with its terms prior to such time. In some circumstances, upon termination of the merger agreement, one of the parties may also be required to pay a termination fee. See the section entitled “The Merger Agreement—Termination” beginning on page 150.

The merger agreement may be terminated in accordance with its terms, and the business combination may not be completed.

The merger agreement contains a number of conditions that must be satisfied or waived prior to the completion of the business combination. There can be no assurance that all of the conditions to the completion of the business combination will be so satisfied or waived. If the conditions to the completion of the business combination are not satisfied or waived, Tidewater and GulfMark will be unable to consummate the business combination and the merger agreement may be terminated. Such conditions include, among others:

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These conditions to the completion of the business combination may not be fulfilled in a timely manner or at all, and, accordingly, the completion of the business combination may be delayed or the business combination may not be completed at all and the merger agreement may be terminated.

In addition, if the business combination is not completed by January 31, 2019 (as extended under certain circumstances), either Tidewater or GulfMark may choose not to proceed with the business combination, and the parties can mutually decide to terminate the merger agreement at any time, before or after the stockholder approvals. In addition, Tidewater and GulfMark may elect to terminate the merger agreement in certain other circumstances. See the section entitled “The Merger Agreement—Termination” beginning on page 150.

Failure to consummate the business combination could negatively impact the price of shares of Tidewater common stock and the price of shares of GulfMark common stock, as well as Tidewater’s and GulfMark’s respective future businesses and financial results.

If the business combination is not completed for any reason, including the failure to receive the required approvals of Tidewater’s and GulfMark’s respective stockholders, Tidewater’s and GulfMark’s respective businesses and financial results may be adversely affected as follows:

In addition to the above risks, if the merger agreement is terminated and either party’s board seeks an alternative transaction, such party’s stockholders cannot be certain that such party will be able to find a party willing to engage in a transaction on more attractive terms than the business combination. If the merger agreement is terminated under specified circumstances, either Tidewater or GulfMark may be required to pay the other party a termination fee. See the section entitled “The Merger Agreement—Termination” beginning on page 150 for a description of these circumstances.

Regulators may impose conditions that are not presently anticipated or cannot be met. In addition, an adverse outcome of any required antitrust or similar review undertaken by a governmental authority could prevent the business combination from being completed or have an adverse effect on Tidewater following the completion of the business combination.

Completion of the business combination is conditioned upon the approval by the NYSE of the listing of the shares of Tidewater common stock to be issued in the first merger upon official notice of issuance and, if applicable, the expiration or termination of the waiting period applicable to the business combination under the HSR Act.

The parties have determined that a notification and filing is not required under the HSR Act. Notwithstanding that determination, the FTC or the Antitrust Division of the DOJ could take action under antitrust laws to prevent or rescind the business combination, require the divestiture of assets, impose conditions on the completion of the

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business combination or require changes to the terms of the business combination or the merger agreement. Such conditions or changes and the process of obtaining regulatory approvals could have the effect of delaying or impeding completion of the business combination or of imposing additional costs or limitations on Tidewater following completion of the business combination, any of which might have an adverse effect on Tidewater following completion of the business combination. Additionally, state attorneys general could seek to block or challenge the completion of the business combination as they deem necessary or desirable in the public interest at any time, including after completion of the business combination. In addition, in some circumstances, a third party could initiate a private action under antitrust laws challenging or seeking to enjoin the business combination, before or after the completion of the business combination.

Other regulatory notices and approvals may be required in connection with the business combination.

Tidewater and GulfMark will be subject to business uncertainties while the business combination is pending, which could adversely affect their respective businesses.

Uncertainty about the effect of the business combination on employees and customers may have an adverse effect on Tidewater and GulfMark. These uncertainties may impair Tidewater’s and GulfMark’s ability to attract, retain and motivate key personnel until the business combination is completed and for a period of time thereafter, and could cause customers and others that deal with Tidewater and GulfMark to seek to change their existing business relationships with Tidewater and GulfMark, respectively. Employee retention at GulfMark may be particularly challenging during the pendency of the business combination, as employees may experience uncertainty about their roles with Tidewater following the business combination. The pursuit of the business combination and the preparation for the integration may also place a significant burden on management and internal resources. The diversion of management’s attention away from day-to-day business concerns and any difficulties encountered in the transition and integration process could adversely affect Tidewater’s and GulfMark’s financial results.

In addition, the merger agreement restricts Tidewater and GulfMark from entering into certain corporate transactions and taking other specified actions without the consent of the other party, and generally requires the parties to continue their operations in the ordinary course, until completion of the business combination. These restrictions may prevent Tidewater and GulfMark from pursuing attractive business opportunities that may arise prior to the completion of the business combination. Please see the section entitled “The Merger Agreement—Interim Operations of Tidewater and GulfMark Pending the Business Combination,” beginning on page 134, for a description of the restrictive covenants to which Tidewater and GulfMark are subject.

Directors and executive officers of GulfMark have interests in the business combination that are different from, or in addition to, the interests of GulfMark stockholders.

Directors and executive officers of GulfMark have interests in the business combination that are different from, or in addition to, the interests of GulfMark stockholders generally. These interests include, among others, the treatment of GulfMark RSUs (including accelerated vesting at the effective time of the first merger of GulfMark RSUs held by directors and potential “double trigger” accelerated vesting of GulfMark RSUs held by executive officers in the event of a qualifying termination or resignation of employment within one year following the first merger effective time), the guaranteed payment of certain 2018 bonus amounts to Messrs. Kneen and Rubio if they remain employed through the closing date of the first merger, general severance payments under Messrs. Kneen’s and Rubio’s respective employment agreements in the event of any termination of employment, Tidewater’s agreement to recommend three individuals designated by GulfMark for election as directors of Tidewater, and rights to ongoing indemnification and insurance coverage. Additionally, as of October 9, 2018, Captain Q and its affiliates hold (i) 853,331 shares of Tidewater common stock, equal to approximately 3.14% of Tidewater common stock issued and outstanding, (ii) 139,207 Tidewater equity warrants (as defined below) and 139,769 Tidewater creditor warrants (as defined below), (iii) a $5,964,056 aggregate principal amount of Tidewater’s New Secured Notes (as defined below), and (iv) swaps representing economic exposure comparable to an additional 25,290 shares of Tidewater common stock and 85,347 Tidewater equity warrants.

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Scott McCarty, a member of the GulfMark Board, is an employee of an affiliate of Captain Q. These interests are described in more detail in the section entitled “The Business Combination—Interests of GulfMark Directors and Executive Officers in the Business Combination” beginning on page 118.

The business combination may not be accretive, and may be dilutive, to Tidewater’s earnings per share and cash flow from operations which may negatively affect the market price of shares of Tidewater common stock.

Earnings per share and cash flow from operations in the future are based on preliminary estimates that may materially change. In addition, future events and conditions could decrease or delay any accretion, result in dilution or cause greater dilution than is currently expected, including:

Any dilution of, or decrease or delay of any accretion to, Tidewater’s earnings per share or cash flow from operations could cause the market price of Tidewater common stock to decline.

Tidewater and GulfMark will incur significant transaction and merger-related costs in connection with the business combination, which may be in excess of those anticipated by Tidewater or GulfMark.

Each of Tidewater and GulfMark has incurred and will incur substantial expenses in connection with the negotiation and completion of the transactions contemplated by the merger agreement, including the costs and expenses of filing, printing and mailing this joint proxy statement/prospectus and all filing and other fees paid to the SEC in connection with the business combination.

Tidewater and GulfMark expect to continue to incur a number of non-recurring costs associated with the completion of the business combination, combining the operations of the two companies and achieving desired synergies. These fees and costs have been, and will continue to be, substantial. The substantial majority of non-recurring expenses will consist of transaction costs related to the business combination and include, among others, employee retention costs, fees paid to financial, legal and accounting advisors, severance and benefit costs and filing fees.

Tidewater and GulfMark will also incur transaction fees and costs related to formulating and implementing integration plans, including facilities and systems consolidation costs and employment-related costs. Additional unanticipated costs may be incurred in connection with the business combination and the integration of the two companies’ businesses. Although Tidewater and GulfMark each expects that the elimination of duplicative costs, as well as the realization of other efficiencies related to the integration of the businesses, should allow Tidewater and GulfMark to offset integration-related costs over time, this net benefit may not be achieved in the near term, or at all. See the risk factor entitled “The integration of GulfMark into Tidewater may not be as successful as anticipated” below.

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The costs described above, as well as other unanticipated costs and expenses could have an adverse effect on the financial condition and operating results of Tidewater following the completion of the business combination.

Many of these costs will be borne by Tidewater and/or GulfMark even if the business combination is not completed.

The opinions of Tidewater’s and GulfMark’s respective financial advisors do not and will not reflect changes in circumstances between the signing of the merger agreement and the completion of the business combination.

Tidewater and GulfMark received opinions from their respective financial advisors in connection with the signing of the merger agreement on July 15, 2018, but have not requested or obtained, and do not intend to request, updated opinions from their respective financial advisors as of the date of this joint proxy statement/prospectus. Changes in the operations and prospects of Tidewater or GulfMark, general market and economic conditions and other factors that may be beyond the control of Tidewater or GulfMark, and on which Tidewater’s and GulfMark’s financial advisors’ opinions were based, may significantly alter the value of Tidewater or GulfMark or the prices of the shares of Tidewater common stock or of the shares of GulfMark common stock by the time the business combination is completed. The opinions do not speak as of the time the business combination will be completed or as of any date other than the dates referenced in such opinions. Because Tidewater and GulfMark do not currently anticipate asking their respective financial advisors to update their opinions, the opinions will not address the fairness of the merger consideration from a financial point of view at the time the business combination is completed. The Tidewater Board’s recommendation that Tidewater stockholders vote “FOR” the Tidewater issuance proposal and the GulfMark Board’s recommendation that GulfMark stockholders vote “FOR” the GulfMark merger proposal, however, are made as of the date of this joint proxy statement/prospectus. For a description of the opinions that Tidewater and GulfMark received from their respective financial advisors, please see the sections entitled “The Business Combination—Opinion of Lazard, Tidewater’s Financial Advisor” and “The Business Combination—Opinion of Evercore, GulfMark’s Financial Advisor” beginning on pages 89 and 104, respectively. A copy of the opinion of Lazard, Tidewater’s financial advisor, is attached as Annex C to this joint proxy statement/prospectus, and a copy of the opinion of Evercore, GulfMark’s financial advisor, is attached as Annex D to this joint proxy statement/prospectus.

Completion of the business combination may trigger change in control or other provisions in certain agreements to which GulfMark is a party.

The completion of the business combination may trigger change in control or other provisions in certain agreements to which GulfMark is a party. If Tidewater and GulfMark are unable to negotiate waivers of those provisions, the counterparties may exercise their rights and remedies under the agreements, potentially terminating the agreements or seeking monetary damages. Even if Tidewater and GulfMark are able to negotiate waivers, the counterparties may require a fee for such waivers or seek to renegotiate the agreements on terms less favorable to GulfMark.

The combined company’s debt may limit its financial flexibility.

As of June 30, 2018, Tidewater had approximately $445 million of outstanding indebtedness. As of June 30, 2018, GulfMark had approximately $100 million of outstanding indebtedness. Tidewater continues to review the treatment of its and GulfMark’s existing indebtedness and, as a part of the transactions contemplated by the merger agreement, Tidewater intends to repay, retire or otherwise terminate GulfMark’s existing indebtedness. There is no guarantee that Tidewater will be able to do so on favorable terms or at all.

Any increase in Tidewater’s indebtedness could have adverse effects on its financial condition and results of operations, including:

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In addition, in connection with executing Tidewater’s business strategies following the completion of the business combination, Tidewater expects to continue to evaluate the possibility of acquiring additional assets and making further strategic investments, and Tidewater may elect to finance these endeavors by incurring additional indebtedness to the extent it is able to do so under its existing debt agreements.

Tidewater’s ability to arrange any additional financing for the purposes described above or otherwise will depend on, among other factors, Tidewater’s financial position and performance, as well as prevailing market conditions and other factors beyond Tidewater’s control. Tidewater cannot assure you that it will be able to obtain such financing on terms acceptable to Tidewater or at all.

The unaudited pro forma condensed consolidated combined financial information and unaudited forecasted financial information included in this joint proxy statement/prospectus is presented for illustrative purposes only and does not represent the actual financial position or results of operations of the combined company following the completion of the business combination. Future results of the combined company may differ, possibly materially, from the unaudited pro forma condensed consolidated combined financial information and unaudited forecasted financial information presented in this joint proxy statement/prospectus.

The unaudited pro forma condensed consolidated combined financial statements and unaudited forecasted financial information contained in this joint proxy statement/prospectus are presented for illustrative purposes only, contain a variety of adjustments, assumptions and preliminary estimates and do not represent the actual financial position or results of operations of Tidewater and GulfMark prior to the completion of the business combination or that of the combined company following the completion of the business combination for several reasons. Specifically, Tidewater and GulfMark have not completed the detailed valuation analyses to arrive at the final estimates of the fair values of the assets to be acquired and liabilities to be assumed and the related allocation of purchase price and the unaudited pro forma condensed consolidated combined financial statements do not reflect the effects of all transaction-related costs and integration costs. See the sections entitled “Unaudited Pro Forma Condensed Consolidated Combined Financial Statements”, and “Notes to Unaudited Pro Forma Condensed Consolidated Combined Financial Statements” beginning on pages 162 and 167, respectively. In addition, the business combination and post-business combination integration process may give rise to unexpected liabilities and costs, including costs associated with the defense and resolution of any litigation or other claims related to the business combination. Unexpected delays in the completion of the business combination or in connection with the post-business combination integration process may significantly increase the related costs and expenses incurred by Tidewater. The actual financial positions and results of operations of Tidewater and GulfMark prior to the completion of the business combination and that of the combined company following the completion of the business combination may be different, possibly materially, from the unaudited pro forma condensed consolidated combined financial statements or forecasted financial information included in this joint proxy statement/prospectus. In addition, the assumptions used in preparing the unaudited pro forma condensed consolidated combined financial statements and forecasted financial information included in this joint proxy statement/prospectus may not prove to be accurate and may be affected by other factors. Any significant changes in the market price of Tidewater common stock may cause a significant change in the purchase price used for Tidewater’s accounting purposes and the unaudited pro forma financial statements contained in this joint proxy statement/prospectus.

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The integration of GulfMark into Tidewater may not be as successful as anticipated.

The business combination involves numerous operational, strategic, financial, accounting, legal, tax and other risks, potential liabilities associated with the acquired businesses and uncertainties related to design, operation and integration of GulfMark’s internal control over financial reporting. Difficulties in integrating GulfMark into Tidewater may result in GulfMark performing differently than expected, in operational challenges or in the failure to realize anticipated expense-related efficiencies. Tidewater’s and GulfMark’s existing businesses could also be negatively impacted by the business combination. Potential difficulties that may be encountered in the integration process include, among other factors:

Tidewater’s results may suffer if it does not effectively manage its expanded operations following completion of the business combination.

Following completion of the business combination, Tidewater’s success will depend, in part, on its ability to manage its expansion, which poses numerous risks and uncertainties, including the need to integrate the operations and business of GulfMark into its existing business in an efficient and timely manner, to combine systems and management controls and to integrate relationships with customers, vendors and business partners.

Even if Tidewater and GulfMark consummate the business combination, Tidewater may fail to realize all of the anticipated benefits of the proposed business combination.

The success of the proposed business combination will depend, in part, on Tidewater’s ability to realize the anticipated benefits and cost savings from combining Tidewater’s and GulfMark’s businesses, including the approximately $30 million of annual cost and operational synergies that Tidewater expects the combined company to realize. The anticipated benefits and cost savings of the proposed business combination may not be realized fully or at all, may take longer to realize than expected, may require more non-recurring costs and expenditures to realize than expected or could have other adverse effects that Tidewater does not currently foresee. Some of the assumptions that Tidewater has made, such as with respect to anticipated operating synergies or the costs associated with realizing such synergies, the benefit from a substantial increase in scale and geographic diversity specifically in the North Sea and the continuation of Tidewater’s investment in its fleet of vessels may not be realized. The integration process may, for each of Tidewater and GulfMark, result in the loss of key employees, the disruption of ongoing businesses or inconsistencies in standards, controls, procedures and policies. There could be potential unknown liabilities and unforeseen expenses associated with the business combination that were not discovered in the course of performing due diligence.

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Uncertainties associated with the business combination may cause a loss of management personnel and other employees, which could adversely affect the future business and operations of the combined company.

Tidewater and GulfMark are dependent on the experience and industry knowledge of their officers and other employees to execute their business plans. Each company’s success until the completion of the business combination and the combined company’s success after the completion of the business combination will depend in part upon the ability of Tidewater and GulfMark to retain management personnel and other employees. Current and prospective employees of Tidewater and GulfMark may experience uncertainty about their roles within the combined company prior to and following the completion of the business combination, which may have an adverse effect on the ability of each of Tidewater and GulfMark to attract or retain management and other personnel. Accordingly, no assurance can be given that the combined company will be able to attract or retain management and other personnel to the same extent that Tidewater and GulfMark have previously been able to attract or retain their own employees.

The market price of shares of Tidewater common stock may decline in the future as a result of the sale of shares of Tidewater common stock held by former GulfMark stockholders or current Tidewater stockholders.

Based on the number of shares of GulfMark common stock outstanding as of July 13, 2018 (other than excluded shares), Tidewater expects to issue, or reserve for future issuance, up to approximately 11,987,730 shares of Tidewater common stock to GulfMark stockholders, GulfMark RSU holders and GulfMark warrant holders in the business combination. Following their receipt of shares of Tidewater common stock as merger consideration in the business combination, former GulfMark stockholders may seek to sell the shares of Tidewater common stock delivered to them. Other Tidewater stockholders may also seek to sell shares of Tidewater common stock held by them following, or in anticipation of, completion of the business combination. These sales (or the perception that these sales may occur), coupled with the increase in the outstanding number of shares of Tidewater common stock, may affect the market for, and the market price of, Tidewater common stock in an adverse manner.

The combined company may record goodwill and may record other intangible assets that could become impaired and result in material non-cash charges to the results of operations of the combined company in the future.

The business combination will be accounted for as an acquisition by Tidewater in accordance with accounting principles generally accepted in the United States. Under the acquisition method of accounting, the assets and liabilities of GulfMark and its subsidiaries will be recorded, as of completion, at their respective fair values and added to those of Tidewater. The reported financial condition and results of operations of Tidewater for periods after completion of the business combination will reflect GulfMark balances and results after completion of the business combination, but will not be restated retroactively to reflect the historical financial position or results of operations of GulfMark and its subsidiaries for periods prior to the completion of the business combination. See the section entitled “Unaudited Pro Forma Condensed Consolidated Combined Financial Statements” beginning on page 162.

Under the acquisition method of accounting, the total purchase price will be allocated to GulfMark’s tangible assets and liabilities and any identifiable intangible assets based on their fair values as of the date of completion of the business combination. The excess of the purchase price over those fair values, if any, would be recorded as goodwill. To the extent the value of tangible assets, goodwill or other identified intangibles becomes impaired, the combined company may incur material non-cash charges relating to such impairment. The combined company’s operating results may be significantly impacted from both the impairment and the underlying trends in the business that triggered the impairment.

The impact of the recent significant federal tax reform on the combined company is uncertain and may significantly affect the operations of the combined company after the business combination.

On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the “Tax Act”). The changes included in the Tax Act are broad and complex. The impact

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of these changes on how the combined company’s earnings are taxed include, among other items, (i) reducing the U.S. federal corporate tax rate from 35% to 21%; (ii) repealing the corporate alternative minimum tax and changing how existing credits can be utilized; (iii) temporarily providing for elective immediate expensing for certain depreciable property; (iv) creating a new limitation on the deductibility of interest expense; and (v) changing rules related to uses and limitations of net operating losses created in tax years beginning after December 31, 2017. Tidewater and GulfMark continue to evaluate the Tax Act and its impact on the combined company’s businesses. It is possible that the Tax Act will be subject to further changes either in a technical corrections bill or entirely new legislation. The overall impact of the Tax Act also depends on the future interpretations and regulations that may be issued by U.S. tax authorities. Tidewater expects there will be further guidance provided by these authorities potentially having a material adverse effect on the combined company’s financial condition or results of operations. The impact of broad proposals or of regulatory issuances on the combined company’s business can vary substantially depending upon the specific changes or further guidance made and how the changes or guidance are implemented by the authorities.

Risks Relating to Tidewater’s Business

The prices for oil and gas affect the level of capital spending by Tidewater’s customers.

Even in a more favorable commodity pricing climate, prices for crude oil and natural gas are highly volatile and extremely sensitive to the respective supply/demand relationship for crude oil and natural gas. The significant decline in crude oil and natural gas prices that began in 2014 has continued to cause many of Tidewater’s customers to significantly reduce drilling, completion and other production activities and related spending on Tidewater’s products and services through the six months ended June 30, 2018. Some industry analysts expect that a further decrease in offshore spending is likely during calendar year 2018 and that any improvements in offshore exploration and development activity would likely not occur until late in calendar year 2019 or early in calendar year 2020. In addition, the reduction in demand from Tidewater’s customers has resulted in an oversupply of the vessels available for service, and such oversupply has substantially reduced the prices Tidewater can charge its customers for its services.

Many factors affect the supply of and demand for crude oil and natural gas and, therefore, influence prices of these commodities, including:

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In recent years, the depressed level of oil and natural gas prices significantly curtailed Tidewater’s customers’ drilling, completion and other production activities and related spending on Tidewater’s services. The energy industry’s level of capital spending is substantially related to current and expected future demand for hydrocarbons and the prevailing commodity prices of crude oil and, to a lesser extent, natural gas. When commodity prices are low, or when Tidewater’s customers believe that they will be low in the future, Tidewater’s customers generally reduce their capital spending budgets for onshore and offshore drilling, exploration and field development. The depressed levels of crude oil and natural gas prices has reduced significantly the energy industry’s level of capital spending and as long as current conditions persist, capital spending and demand for Tidewater’s services may remain similarly depressed. It is difficult to predict how long the current commodity price conditions will continue, or to what extent low commodity prices will affect Tidewater’s business. Because a prolonged material downturn in crude oil and natural gas prices and/or perceptions of long-term lower commodity prices can negatively impact the development plans of exploration and production companies given the long-term nature of large-scale development projects, a downturn of any such duration would likely result in a significant decline in demand for offshore support services. Declining or continuing depressed oil and natural gas prices may result in negative pressures on:

Moreover, higher commodity prices will not necessarily translate into increased demand for offshore support services or sustained higher pricing for offshore support vessel services, in part because customer demand is based on future commodity price expectations and not solely on current prices. Additionally, increased commodity demand may in the future be satisfied by land-based energy resource production and any increased demand for offshore support vessel services can be more than offset by an increased supply of offshore support vessels resulting from the reactivation of currently idle offshore support vessels and/or the construction of additional offshore support vessels.

Crude oil pricing volatility has increased in recent years as crude oil has emerged as a widely-traded financial asset class. To the extent speculative trading of crude oil causes excessive crude oil pricing volatility, Tidewater’s results of operations could potentially be negatively impacted if such price volatility affects spending and investment decisions of offshore exploration, development and production companies.

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Tidewater’s customer base has undergone consolidation, and additional consolidation is possible.

Oil and natural gas companies and other energy companies and energy services companies have undergone consolidation, and additional consolidation is possible. Consolidation reduces the number of customers for Tidewater’s equipment, and may negatively affect exploration, development and production activity as consolidated companies focus, at least initially, on increasing efficiency and reducing costs and may delay or abandon exploration activity with less promise. Such activity could adversely affect demand for Tidewater’s offshore services.

The high level of competition in the offshore marine service industry could negatively impact pricing for Tidewater’s services.

Tidewater operates in a highly competitive industry, which could depress charter and utilization rates and adversely affect its financial performance. Tidewater competes for business with Tidewater’s competitors on the basis of price; reputation for quality service; quality, suitability and technical capabilities of its vessels; availability of vessels; safety and efficiency; cost of mobilizing vessels from one market to a different market; and national flag preference. In addition, competition in international markets may be adversely affected by regulations requiring, among other things, local construction, flagging, ownership or control of vessels, the awarding of contracts to local contractors, the employment of local citizens and/or the purchase of supplies from local vendors.

Tidewater derives a significant amount of revenue from a relatively small number of customers.

For the periods from August 1, 2017 through December 31, 2017 (Successor, which refers to Tidewater post-reorganization), April 1, 2017 through July 31, 2017 (Predecessor, which refers to Tidewater pre-reorganization), and the twelve months ended March 31, 2017 (Predecessor), the five largest customers accounted for approximately 45%, 48% and 53%, respectively, of Tidewater’s total revenues, while the 10 largest customers accounted for approximately 64%, 69% and 75%, respectively, of Tidewater’s total revenues. While it is normal for Tidewater’s customer base to change over time as its time charter contracts expire and are replaced, Tidewater’s results of operations, financial condition and cash flows could be materially adversely affected if one or more of these customers were to decide to interrupt or curtail their activities, in general, or their activities with Tidewater, terminate their contracts with Tidewater, fail to renew existing contracts, and/or refuse to award new contracts.

The rise in production of unconventional crude oil and gas resources could increase supply without a commensurate growth in demand which would negatively impact oil and gas prices.

The rise in production of unconventional crude oil and gas resources in North America and the commissioning of a number of new large Liquefied Natural Gas (LNG) export facilities around the world have contributed to an over-supplied natural gas market. Production from unconventional resources has increased as drilling efficiencies have improved, lowering the costs of extraction. There has also been a buildup of crude oil inventories in the United States in part due to the increased development of unconventional crude oil resources. Prolonged increases in the worldwide supply of crude oil and natural gas, whether from conventional or unconventional sources, without a commensurate growth in demand for crude oil and natural gas will likely continue to weigh on the price of crude oil and natural gas. A prolonged period of low crude oil and natural gas prices would likely have a negative impact on development plans of exploration and production companies, which in turn, may result in a decrease in demand for offshore support vessel services.

Uncertain economic conditions may lead Tidewater’s customers to postpone capital spending.

Uncertainty about future global economic market conditions makes it challenging to forecast operating results and to make decisions about future investments. The success of Tidewater’s business is both directly and

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indirectly dependent upon conditions in the global financial and credit markets that are outside of Tidewater’s control and difficult to predict. Uncertain economic conditions may lead Tidewater’s customers to postpone capital spending in response to tighter credit markets and reductions in Tidewater’s customers’ income or asset values. Similarly, when lenders and institutional investors reduce, and in some cases, cease to provide funding to corporate and other industrial borrowers, the liquidity and financial condition of Tidewater and Tidewater’s customers can be adversely impacted. These factors may also adversely affect Tidewater’s liquidity and financial condition. Factors such as interest rates, availability of credit, inflation rates, economic uncertainty, changes in laws (including laws relating to taxation), trade barriers, commodity prices, currency exchange rates and controls, and national and international political circumstances (including wars, terrorist acts, security operations, and seaborne refugee issues) can have a material negative effect on Tidewater’s business, revenues and profitability.

An increase in vessel supply without a corresponding increase in the working offshore rig count could exacerbate the industry’s currently oversupplied condition.

Over the past decade, the combination of historically high commodity prices and technological advances resulted in significant growth in deepwater exploration, field development and production. During this time, construction of offshore vessels increased significantly in order to meet projected requirements of customers and potential customers. Excess offshore support vessel capacity usually exerts downward pressure on charter day rates. Excess capacity can occur when newly constructed vessels enter the worldwide offshore support vessel market and also when vessels migrate between markets. A discussion about Tidewater’s vessel fleet and vessel construction programs appears in the “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Vessel Count, Dispositions, Acquisitions and Construction Programs for the Six Months Ended June 30, 2018 and 2017” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Vessel Count, Dispositions, Acquisitions and Construction Programs for the Nine Months Ended December 31, 2017 and 2016” sections of this joint proxy statement/prospectus.

The offshore support vessel market has approximately 240 new-build offshore support vessels (deepwater PSVs, deepwater AHTS vessels and towing-supply vessels only) either under construction, on order or planned as of June 2018, which may be delivered to the worldwide offshore support vessel market primarily over the next 12 to 24 months, according to IHS-Markit. The current worldwide fleet of these classes of vessels is estimated at 3,520 vessels, according to the same source. An increase in vessel capacity without a corresponding increase in the working offshore rig count could exacerbate the industry’s currently oversupplied condition which may have the effect of lowering charter rates and utilization rates, which, in turn, could result in lower revenues to Tidewater.

In addition, the provisions of U.S. shipping laws restricting engagement of U.S. coastwise trade to vessels controlled by U.S. citizens may from time to time be circumvented by foreign competitors that seek to engage in trade reserved for vessels controlled by U.S. citizens and otherwise qualifying for coastwise trade. A repeal, suspension or significant modification of U.S. shipping laws, or the administrative erosion of their benefits, permitting vessels that are either foreign-flagged, foreign-built, foreign-owned, foreign-controlled or foreign-operated to engage in the U.S. coastwise trade, could also result in excess vessel capacity and increased competition, especially for Tidewater’s vessels that operate in the United States.

Tidewater operates in various regions throughout the world and is exposed to many risks inherent in doing business in countries other than the United States.

Tidewater operates in various regions throughout the world and is exposed to many risks inherent in doing business in countries other than the United States, some of which have recently become more pronounced. Tidewater’s customary risks of operating internationally include political and economic instability within the host country; possible vessel seizures or nationalization of assets and other governmental actions by the host country, including enforcement of customs, immigration or other laws that are not well developed or consistently enforced; foreign government regulations that favor or require the awarding of contracts to local competitors; an inability to recruit, retain or obtain work visas for workers of international operations; difficulties or delays in

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collecting customer and other accounts receivable; changing taxation policies; fluctuations in currency exchange rates; foreign currency revaluations and devaluations; restrictions on converting foreign currencies into U.S. dollars; expatriating customer and other payments made in jurisdictions outside of the United States; and import/export quotas and restrictions or other trade barriers, most of which are beyond the control of Tidewater. See “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Legal Proceedings” beginning on page 260 and “Additional Information About Tidewater—Challenges Tidewater Confronts as an International Offshore Vessel Company—Sonatide Joint Venture” beginning on page 199, and Note (14) of “Notes to Consolidated Financial Statements” included in this joint proxy statement/prospectus for a discussion of Tidewater’s Sonatide joint venture in Angola. While Tidewater no longer operates in Venezuela, Tidewater has substantial operations in Brazil, Mexico, Saudi Arabia, Angola, Nigeria and along the west coast of Africa, which generate a large portion of Tidewater’s revenue, where Tidewater is exposed to the risks described above.

Tidewater is also subject to acts of piracy and kidnappings that put Tidewater’s assets and personnel at risk. The increase in the level of these criminal or terrorist acts over the last several years has been well-publicized.

As a marine services company that operates in offshore, coastal or tidal waters in challenging areas, Tidewater is particularly vulnerable to these kinds of unlawful activities. Although Tidewater takes what it considers to be prudent measures to protect its personnel and assets in markets that present these risks, including solicitation of advice from third-party experts, Tidewater has confronted these kinds of incidents in the past, and there can be no assurance it will not be subjected to them in the future.

The continued threat of terrorist activity, other acts of war or hostility and civil unrest have significantly increased the risk of political, economic and social instability in some of the geographic areas in which Tidewater operates. It is possible that further acts of terrorism or civil unrest may be directed against the United States domestically or abroad, and such acts of terrorism or civil unrest could be directed against properties and personnel of U.S. headquartered companies such as Tidewater. To date, Tidewater has not experienced any material adverse effects on its results of operations and financial condition as a result of terrorism, political instability, civil unrest or war.

Tidewater may not be able to generate sufficient cash flow to meet its debt service and other obligations.

Tidewater’s ability to make payments on its indebtedness and to fund its operations depends on Tidewater’s ability to generate cash in the future. This, to a large extent, is subject to conditions in the oil and natural gas industry, including commodity prices, demand for its services and the prices Tidewater is able to charge for its services, general economic and financial conditions, competition in the markets in which Tidewater operates, the impact of legislative and regulatory actions on how Tidewater conducts its business and other factors, all of which are beyond its control.

Lower levels of offshore exploration and development activity and spending by Tidewater’s customers globally has had a direct and significant impact on its financial performance, financial condition and financial outlook.

Tidewater may record additional losses or impairment charges related to its vessels.

Tidewater reviews the vessels in Tidewater’s active fleet for impairment whenever events occur or changes in circumstances indicate that the carrying amount of an asset group may not be recoverable and Tidewater also performs a review of its stacked vessels not expected to return to active service whenever changes in circumstances indicate that the carrying amount of a vessel may not be recoverable. Tidewater has recorded impairment charges of $16.8 million, $184.7 million and $419.9 million, during the period from August 1, 2017 through December 31, 2017 (Successor), the period from April 1, 2017 through July 31, 2017 (Predecessor) and the nine-month period ended December 31, 2016 (Predecessor), respectively. In the event that offshore exploration and production industry conditions continue to deteriorate, or persist at current levels, Tidewater

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could be subject to additional vessel impairments in future periods. An impairment loss on Tidewater’s property and equipment exists when the estimated undiscounted cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount and the carrying amount exceeds its fair value. Any impairment loss recognized represents the excess of the asset’s carrying value over the estimated fair value. As part of this analysis, Tidewater makes assumptions and estimates regarding future market conditions. To the extent actual results do not meet Tidewater’s estimated assumptions it may take an impairment loss in the future. Additionally, there can be no assurance that Tidewater will not have to take additional impairment charges in the future, if the currently depressed market conditions persist.

There are uncertainties in identifying and/or integrating acquisitions.

Although acquisitions have historically been an element of Tidewater’s business strategy, Tidewater cannot assure that it will be able to identify and acquire acceptable acquisition candidates on terms favorable to Tidewater in the future. Tidewater may be required to incur substantial indebtedness or issue equity to finance future acquisitions. Such additional debt service requirements may impose a significant burden on Tidewater’s results of operations and financial condition, and any equity issuance could have a dilutive impact on Tidewater’s stockholders. Tidewater cannot be certain that it will be able to successfully consolidate the operations and assets of any acquired business with its own business. Acquisitions may not perform as expected when the transaction was completed and may be dilutive to Tidewater’s overall operating results. In addition, Tidewater’s management may not be able to effectively manage a substantially larger business or successfully operate a new line of business.

Tidewater may not be able to successfully enter or grow a new line of business.

Historically, Tidewater’s operations and acquisitions focused primarily on offshore marine vessel services for the oil and gas industry. Entry into, or further development of, lines of business in which Tidewater has not historically operated may expose it to business and operational risks that are different from those Tidewater has experienced historically. Tidewater’s management may not be able to effectively manage these additional risks or implement successful business strategies in new lines of business. Additionally, Tidewater’s competitors in these lines of business may possess substantially greater operational knowledge, resources and experience than Tidewater.

Tidewater may have disruptions or disagreements with its foreign joint venture partners, which could lead to an unwinding of the joint venture.

Tidewater operates in several foreign areas through joint ventures with local companies, in some cases as a result of local laws requiring local company ownership. While the joint venture partner may provide local knowledge and experience, entering into joint ventures often requires Tidewater to surrender a measure of control over the assets and operations devoted to the joint venture, and occasions may arise when Tidewater does not agree with the business goals and objectives of its partner, or other factors may arise that make the continuation of the relationship unwise or untenable. Any such disagreements or discontinuation of the relationship could disrupt Tidewater’s operations, put assets dedicated to the joint venture at risk, or affect the continuity of its business. If Tidewater is unable to resolve issues with a joint venture partner, Tidewater may decide to terminate the joint venture and either locate a different partner and continue to work in the area or seek opportunities for Tidewater’s assets in another market. The unwinding of an existing joint venture could prove to be difficult or time-consuming, and the loss of revenue related to the termination or unwinding of a joint venture and costs related to the sourcing of a new partner or the mobilization of assets to another market could adversely affect Tidewater’s financial condition, results of operations or cash flows. Please refer to “Additional Information About Tidewater—Business” beginning on page 188 and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” beginning on page 204 for additional discussion of Tidewater’s Sonatide joint venture in Angola and Tidewater’s joint venture in Nigeria, respectively.

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Tidewater’s international operations expose it to currency devaluation and fluctuation risk.

As a global company, Tidewater’s international operations are exposed to foreign currency exchange rate risks on all charter hire contracts denominated in foreign currencies. For some of Tidewater’s international contracts, a portion of the revenue and local expenses is incurred in local currencies and Tidewater is at risk of changes in the exchange rates between the U.S. dollar and foreign currencies. In some instances, Tidewater receives payments in currencies which are not easily traded and may be illiquid. Tidewater generally does not (and in some cases cannot) hedge against any foreign currency rate fluctuations associated with foreign currency contracts that arise in the normal course of business, which exposes Tidewater to the risk of exchange rate losses. Gains and losses from the revaluation of Tidewater’s monetary assets and liabilities denominated in currencies other than the U.S. dollar are included in its consolidated statements of operations. Foreign currency fluctuations may cause the U.S. dollar value of Tidewater’s non-U.S. results of operations and net assets to vary with exchange rate fluctuations. This could have a negative impact on Tidewater’s results of operations and financial position. In addition, fluctuations in currencies relative to currencies in which the earnings are generated may make it more difficult to perform period-to-period comparisons of Tidewater’s reported results of operations.

To minimize the financial impact of these items, Tidewater attempts to contract a significant majority of its services in U.S. dollars and, when feasible, Tidewater attempts to not maintain large, non-U.S. dollar-denominated cash balances. In addition, Tidewater attempts to minimize the financial impact of these risks by matching the currency of Tidewater’s operating costs with the currency of revenue streams when considered appropriate. Tidewater monitors the currency exchange risks associated with all contracts not denominated in U.S. dollars.

As of June 30, 2018, Tidewater’s joint venture in Angola, Sonatide, maintained the equivalent of approximately $43 million of Angolan kwanza-denominated deposits in Angolan banks, largely related to customer receipts that had not yet been converted to U.S. dollars, expatriated and then remitted to Tidewater. A devaluation in the Angolan kwanza relative to the U.S. dollar would result in foreign exchange losses for Sonatide to the extent the Angolan kwanza-denominated asset balances were in excess of kwanza-denominated liabilities, 49% under the current joint venture structure would be borne by Tidewater. In addition, the joint venture structure could be modified by mutual agreement of Tidewater and its partner, which may increase the foreign exchange losses borne by Tidewater.

Tidewater’s insurance coverage and contractual indemnity protections may not be sufficient to protect Tidewater under all circumstances or against all risks.

Tidewater’s operations are subject to the hazards inherent in the offshore oilfield business. These include blowouts, explosions, fires, collisions, capsizings, sinkings, groundings and severe weather conditions. Some of these events could be the result of (or exacerbated by) mechanical failure or navigation or operational errors. These hazards could result in personal injury and loss of life, severe damage to or destruction of property and equipment (including to the property and equipment of third parties), pollution or environmental damage and suspension of operations, increased costs and loss of business. Damages arising from such occurrences may result in lawsuits alleging large claims, and Tidewater may incur substantial liabilities or losses as a result of these hazards.

Tidewater carries what it considers to be prudent levels of liability insurance, and Tidewater’s vessels are generally insured for their estimated market value against damage or loss, including war, terrorism acts and pollution risks. While Tidewater maintains insurance protection and seeks to obtain indemnity agreements from its customers requiring the customers to hold Tidewater harmless from some of these risks, Tidewater’s insurance and contractual indemnity protection may not be sufficient or effective to protect it under all circumstances or against all risks. Tidewater’s insurance coverages are subject to deductibles and certain exclusions. Tidewater does not directly or fully insure for business interruption. The occurrence of a significant event not fully insured or indemnified against or the failure of a customer to meet its indemnification obligations to Tidewater could have a material and adverse effect on Tidewater’s results of operations and financial

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condition. Additionally, while Tidewater believes that it should be able to maintain adequate insurance in the future at rates considered commercially acceptable, Tidewater cannot guarantee that such insurance will continue to be available at commercially acceptable rates given the markets in which it operates.

With Tidewater’s extensive international operations, it is subject to certain compliance risks under the Foreign Corrupt Practices Act or similar worldwide anti-bribery laws.

Tidewater’s global operations require it to comply with a number of U.S. and international laws and regulations, including those involving anti-bribery and anti-corruption. As a U.S. corporation, Tidewater is subject to the regulations imposed by the Foreign Corrupt Practices Act (“FCPA”), which generally prohibits U.S. companies and their intermediaries from making improper payments to foreign officials for the purpose of obtaining or keeping business or obtaining an improper business benefit. Tidewater has adopted proactive procedures to promote compliance with the FCPA, but it may be held liable for actions taken by local partners or agents even though these partners or agents may themselves not be subject to the FCPA. Any determination that Tidewater has violated the FCPA (or any other applicable anti-bribery laws in countries in which Tidewater does business) could have a material adverse effect on its business and business reputation, as well as Tidewater’s results of operations, and cash flows.

There may be changes to complex and developing laws and regulations to which Tidewater is subject that would increase its cost of compliance and operational risk.

Tidewater’s operations are subject to many complex and burdensome laws and regulations. Stringent federal, state, local and foreign laws and regulations governing worker health and safety and the manning, construction and operation of vessels significantly affect its operations. Many aspects of the marine industry are subject to extensive governmental regulation by the United States Coast Guard, the United States Customs and Border Protection, and their foreign equivalents; as well as to standards imposed by private industry organizations such as the American Bureau of Shipping, the Oil Companies International Marine Forum, and the International Marine Contractors Association.

Further, many of the countries in which Tidewater operates have laws, regulations and enforcement systems that are less well developed than the laws, regulations and enforcement systems of the United States, and the requirements of these systems are not always readily discernible even to experienced and proactive participants. These countries’ laws can be unclear, and, the application and enforcement of these laws and regulations can be unpredictable and subject to frequent change or reinterpretation. Sometimes governments may apply such changes or reinterpretations with retroactive effect, and may impose associated taxes, fees, fines or penalties on Tidewater based on that reinterpretation or retroactive effect. While Tidewater endeavors to comply with applicable laws and regulations, its compliance efforts might not always be wholly successful, and failure to comply may result in administrative and civil penalties, criminal sanctions, imposition of remedial obligations or the suspension or termination of Tidewater’s operations. These laws and regulations may expose Tidewater to liability for the conduct of, or conditions caused by, others, including charterers or third party agents. Moreover, these laws and regulations could be changed or be interpreted in new, unexpected ways that substantially increase costs that Tidewater may not be able to pass along to its customers. Any changes in laws, regulations or standards imposing additional requirements or restrictions could adversely affect Tidewater’s financial condition, results of operations or cash flows.

There may be changes in the laws governing U.S. taxation of foreign source income.

Tidewater operates globally through various subsidiaries which are subject to changes in applicable tax laws, treaties or regulations in the jurisdictions in which it conducts its business, including laws or policies directed toward companies organized in jurisdictions with low tax rates. Tidewater determines its income tax expense based on its interpretation of the applicable tax laws and regulations in effect in each jurisdiction for the period during which Tidewater operates and earns income. A material change in the tax laws, tax treaties, regulations or

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accounting principles, or interpretation thereof, in one or more countries in which it conducts business, or in which Tidewater is incorporated or a resident of, could result in a higher effective tax rate on its worldwide earnings, and such change could be significant to its financial results. In addition, Tidewater’s overall effective tax rate could be adversely and suddenly affected by lower than anticipated earnings in countries with lower statutory rates and higher than anticipated earnings in countries with higher statutory rates, or by changes in the valuation of Tidewater’s deferred tax assets and liabilities.

Approximately 90% of Tidewater’s revenues and a majority of its net income are generated by Tidewater’s operations outside of the United States. Beginning in the quarter ended June 30, 2015, Tidewater uses a discrete effective tax rate method to calculate taxes for interim periods. Tidewater determined that due to the level of volatility and unpredictability of earnings in our industry, both overall and by jurisdiction, use of the discrete method will continue to be proper until facts and circumstances change.

Changes in applicable tax regulations could negatively affect Tidewater’s financial results. Tidewater is subject to taxation in the U.S. and numerous foreign jurisdictions. Tidewater’s financial results may differ from the estimates provided elsewhere in this joint proxy statement/prospectus, possibly materially, due to, among other things, the Tax Act, changes in interpretations of the Tax Act, any legislative action to address questions that arise because of the Tax Act, any changes in accounting standards for income taxes or related interpretations in response to the Tax Act, or any updates or changes to estimates Tidewater has utilized to calculate the transition impacts. Additionally, longstanding international tax norms that determine each country’s jurisdiction to tax cross-border international trade are evolving as a result of the Base Erosion and Profit Shifting reporting requirements recommended by the G8, G20 and Organization for Economic Cooperation and Development. As these and other tax laws and related regulations change, Tidewater’s financial results could be materially impacted. Given the unpredictability of these possible changes and their potential interdependency, it is very difficult to assess whether the overall effect of such potential tax changes would be cumulatively positive or negative for Tidewater’s earnings and cash flow, but such changes could adversely impact its financial results.

In addition, Tidewater’s income tax returns are subject to review and examination by the U.S. Internal Revenue Service (“IRS”) and other tax authorities where tax returns are filed. Tidewater routinely evaluates the likelihood of adverse outcomes resulting from these examinations to determine the adequacy of Tidewater’s provision for taxes. Tidewater does not recognize the benefit of income tax positions it believes are more likely than not to be disallowed upon challenge by a tax authority. If any tax authority successfully challenges Tidewater’s operational structure or intercompany transfer pricing policies, or if the terms of certain income tax treaties were to be interpreted in a manner that is adverse to its structure, or if Tidewater loses a material tax dispute in any country, Tidewater’s effective tax rate on its worldwide earnings could increase, and Tidewater’s financial condition and results of operations could be materially and adversely affected.

Any changes in environmental regulations could increase the cost of energy and future production of oil and gas.

Tidewater’s operations are subject to federal, state, local and international laws and regulations that control the discharge of pollutants into the environment or otherwise relate to environmental protection. Compliance with such laws and regulations may require installation of costly equipment, increased manning or operational changes. Some environmental laws impose strict liability for remediation of spills and releases of oil and hazardous substances, which could subject Tidewater to liability without regard to whether it was negligent or at fault.

A variety of regulatory developments, proposals and requirements have been introduced (and in some cases enacted) in the U.S. and various other countries that are focused on restricting the emission of carbon dioxide, methane and other gases. Notwithstanding the current downturn in the oil industry punctuated by lessened demand and lower oil prices, any such regulations could ultimately result in the increased cost of energy as well as environmental and other costs, and capital expenditures could be necessary to comply with the limitations.

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These developments may have an adverse effect on future production and demand for hydrocarbons such as crude oil and natural gas in areas of the world where Tidewater’s customers operate and thus adversely affect future demand for Tidewater’s offshore support vessels and other assets, which are highly dependent on the level of activity in offshore oil and natural gas exploration, development and production markets. In addition, the increased regulation of environmental emissions may create greater incentives for the use of alternative energy sources. Unless and until regulations are implemented and their effects are known, Tidewater cannot reasonably or reliably estimate their impact on its financial condition, results of operations and ability to compete. However, any long term material adverse effect on the crude oil and natural gas industry may adversely affect Tidewater’s financial condition, results of operations and cash flows.

Adoption of climate change and greenhouse gas restrictions could increase the cost of energy and future production of oil and gas.

Due to concern over the risk of climate change, a number of countries have adopted, or are considering the adoption of, regulatory frameworks to reduce greenhouse gas emissions. These include adoption of cap and trade regimes, carbon taxes, restrictive permitting, increased efficiency standards, and incentives or mandates for renewable energy. These requirements could make Tidewater’s customer’s products more expensive and reduce demand for hydrocarbons, as well as shift hydrocarbon demand toward relatively lower-carbon sources such as natural gas, any of which may reduce demand for its services.

Tidewater may be subject to additional unionization efforts, new collective bargaining agreements or work stoppages.

In locations in which it is required to do so, Tidewater has union workers, subject to collective bargaining agreements, that are periodically in negotiation. These negotiations could result in higher personnel expenses, other increased costs, or increased operational restrictions. Further, efforts have been made from time to time to unionize other portions of Tidewater’s workforce, including its U.S. Gulf of Mexico employees. Tidewater has also been subjected to threatened strikes or work stoppages and other labor disruptions in certain countries. Additional unionization efforts, new collective bargaining agreements or work stoppages could materially increase Tidewater’s costs and operating restrictions, reduce its revenues, or limit its flexibility.

Risks Relating to Tidewater’s Securities

Tidewater common stock is subject to restriction on foreign ownership and possible required divestiture by non-U.S. Citizen stockholders.

Certain of Tidewater’s operations are conducted in the U.S. coastwise trade and are governed by the U.S. federal law commonly known as the Jones Act. The Jones Act restricts waterborne transportation of goods and passengers between points in the United States (known as coastwise trade) to vessels owned and controlled by “U.S. Citizens” as defined thereunder (which Tidewater refers to as U.S. Citizens). Tidewater could lose the privilege of owning and operating vessels in the coastwise trade if non-U.S. Citizens were to own or control, in the aggregate, more than 25% of common stock in Tidewater. Such loss could have a material adverse effect on Tidewater’s results of operations.

The Tidewater certificate of incorporation and the Tidewater bylaws authorize the Tidewater Board to establish with respect to any class or series of capital stock of Tidewater certain rules, policies and procedures, including procedures with respect to transfer of shares, to ensure compliance with the Jones Act. In order to provide a reasonable margin for compliance with the Jones Act, the Tidewater certificate of incorporation provides that, all non-U.S. Citizens in the aggregate may own up to 24% of the outstanding shares of common stock and any individual non-U.S. Citizen may own up to 4.9% of the outstanding shares of common stock.

On the Emergence Date (as defined under the section entitled “Additional Information About Tidewater—Reorganization of Tidewater”), approximately 22% of Tidewater’s outstanding common stock was owned by

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non-U.S. Citizens. At and during such time that the permitted limit of ownership by non-U.S. Citizens is reached with respect to shares of common stock, as applicable, Tidewater will be unable to issue any further shares of such class of common stock or approve transfers of such class of common stock to non-U.S. Citizens. Any purported transfer of shares of Tidewater common stock in violation of these ownership provisions will be ineffective to transfer the common stock or any voting, dividend or other rights associated with them. The existence and enforcement of these requirements could have an adverse impact on the liquidity or market value of Tidewater’s equity securities in the event that U.S. Citizens were unable to transfer Tidewater shares to non-U.S. Citizens. Furthermore, under certain circumstances, this ownership requirement could discourage, delay or prevent a change of control of Tidewater.

The market price of Tidewater’s securities is subject to volatility.

Upon emergence from the Chapter 11 proceeding, Tidewater’s old common stock was canceled and Tidewater issued new common stock. The market price of Tidewater common stock could be subject to wide fluctuations in response to, and the level of trading that develops with Tidewater common stock may be affected by, numerous factors beyond Tidewater’s control such as, Tidewater’s limited trading history subsequent to Tidewater’s emergence from bankruptcy, on occasion Tidewater’s securities are thinly traded, the lack of comparable historical financial information due to Tidewater’s adoption of fresh-start accounting, actual or anticipated variations in Tidewater’s operating results and cash flow, business conditions in Tidewater’s markets and the general state of the securities markets and the market for energy-related stocks, as well as general economic and market conditions and other factors that may affect Tidewater’s future results, including those described in this joint proxy statement/prospectus.

Because Tidewater currently has no plans to pay cash dividends or other distributions on Tidewater common stock, you may not receive any return on investment unless you sell your common stock for a price greater than that which you paid for it.

Tidewater currently does not expect to pay any cash dividends or other distributions on Tidewater common stock in the foreseeable future. Any future determination to pay cash dividends or other distributions on Tidewater common stock will be at the sole discretion of the Tidewater Board and, if Tidewater elects to pay such dividends in the future, Tidewater may reduce or discontinue entirely the payment of such dividends at any time. The Tidewater Board may take into account general and economic conditions, Tidewater’s financial condition and operating results, Tidewater’s available cash and current and anticipated cash needs, capital requirements, agreements governing any existing and future indebtedness of Tidewater or its subsidiaries may incur and other contractual, legal, tax and regulatory restrictions and implications on the payment of dividends by Tidewater to its stockholders, and such other factors as the Tidewater Board may deem relevant. As a result, you may not receive any return on an investment in Tidewater common stock unless you sell Tidewater common stock for a price greater than that which you paid for it.

Tidewater’s ability to raise capital in the future may be limited, which could make it unable to fund Tidewater’s capital requirements.

Tidewater’s business and operations may consume cash more quickly than it anticipates potentially impairing its ability to make capital expenditures to maintain Tidewater’s fleet and other assets in suitable operating condition. If Tidewater’s cash flows from operating activities are not sufficient to fund capital expenditures, it would be required to further reduce these expenditures or to fund capital expenditures through debt or equity issuances or through alternative financing plans or selling assets. If adequate funds are not available on acceptable terms, Tidewater may be unable to fund its capital requirements. Tidewater’s ability to raise debt or equity capital or to refinance or restructure existing debt arrangements are limited by its existing debt arrangements and will depend on the condition of the capital markets and Tidewater’s financial condition at such time, among other things. Any limitations in Tidewater’s ability to finance future capital expenditures may limit Tidewater’s ability to respond to changes in customer preferences, technological change and other market conditions, which may diminish Tidewater’s competitive position within its sector.

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If Tidewater issues additional equity securities, existing stockholders will experience dilution. The Tidewater certificate of incorporation permits the Tidewater Board to issue preferred stock, which could have rights and preferences senior to those of Tidewater common stock. Because Tidewater’s decision to issue securities in any future offering will depend on market conditions and other factors beyond its control, Tidewater cannot predict or estimate the amount, timing or nature of its future offerings. Thus, Tidewater’s security holders bear the risk of its future securities offerings reducing the market price of Tidewater common stock or other securities, diluting their interest or being subject to rights and preferences senior to their own.

If securities analysts do not publish research or reports about Tidewater’s business or if they downgrade or provide negative outlook on Tidewater’s securities or its industry, the market price of Tidewater’s securities and its trading volume could decline.

The trading markets for Tidewater’s securities rely in part on the research and reports that industry or financial analysts publish about Tidewater or its business. Tidewater does not control these analysts. Furthermore, if one or more of the analysts who do cover Tidewater downgrade or provide negative outlook on Tidewater’s securities or its industry or the stock of any of Tidewater’s competitors, or publish inaccurate or unfavorable research about Tidewater’s business, the price of Tidewater’s securities could decline. If one or more of these analysts ceases coverage of Tidewater’s business or fails to publish reports on Tidewater regularly, Tidewater could lose visibility in the market, which in turn could cause the price or trading volume of Tidewater’s securities to decline.

Anti-takeover provisions and limitations on foreign ownership in Tidewater’s organizational documents could delay or prevent a change of control.

Certain provisions of the Tidewater certificate of incorporation and the Tidewater bylaws may have an anti-takeover effect and may delay, defer or prevent a merger, acquisition, tender offer, takeover attempt or other change of control transaction that a stockholder might consider in its best interest, including those attempts that might result in a premium over the market price for the shares held by Tidewater’s stockholders. These provisions provide for, among other things:

These anti-takeover provisions and foreign ownership limitations could discourage, delay or prevent a transaction involving a change in control of Tidewater, including actions that Tidewater’s stockholders may deem advantageous, or negatively affect the trading price of Tidewater common stock and other securities. These provisions could also discourage proxy contests and make it more difficult for you and other stockholders to elect directors of your choosing and to cause Tidewater to take other corporate actions you desire.

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The exercise of all or any number of outstanding warrants or the issuance of stock-based awards may dilute your holding of shares of Tidewater common stock.

Tidewater has a significant number of securities providing for the right to purchase Tidewater common stock. Investors could be subject to increased dilution upon the exercise of Tidewater’s creditor warrants on a nominal exercise price subject to Jones Act-related foreign ownership restrictions, and the exercise of Tidewater’s Series A Warrants and Series B Warrants. On July 31, 2017, the date of Tidewater’s emergence from Chapter 11 bankruptcy, Tidewater issued 18,456,186 shares of common stock in the reorganized company, 2,432,432 Series A Warrants with a strike price of $57.06 per warrant, 2,629,657 Series B Warrants with a strike price of $62.28 per warrant and 7,684,453 creditor warrants (with an additional 3,859,361 of creditor warrants issuable related to the sale leaseback claims which have since been resolved). As of June 30, 2018, Tidewater had 3,924,441 shares of common stock issuable upon the exercise of the creditor warrants, with an exercise price of $0.001 per share. Tidewater also has up to 2,432,432 and 2,629,657 shares of common stock issuable upon the exercise of the 2,432,432 Series A Warrants and 2,629,657 Series B Warrants with exercise prices of $57.06 and $62.28, respectively.

Additionally, a total of 3,048,877 shares of Tidewater common stock were reserved for issuance under the 2017 Stock Incentive Plan as equity-based awards to Tidewater employees, directors and certain other persons. As of June 30, 2018, 1,471,423 restricted stock units have been granted under the 2017 Stock Incentive Plan and are subject to vesting requirements. The grant or vesting of equity awards, including any that Tidewater may grant in the future, and the exercise of warrants and the subsequent sale of shares of common stock issued thereby, could have an adverse effect on the market for Tidewater common stock, including the price that an investor could obtain for their shares. Investors may experience dilution in the value of their investment upon the exercise of the warrants and any shares subject to equity awards that may be granted or issued pursuant to the 2017 Stock Incentive Plan.

There may be a limited trading market for Tidewater’s creditor warrants and you may have difficulty trading and obtaining quotations for creditor warrants.

While there are trades of Tidewater’s creditor warrants, there is currently no active trading market for the creditor warrants and there can be no assurance that an active trading market will develop. The lack of an active market may impair your ability to sell your creditor warrants at the time you wish to sell them or at a price that you consider reasonable. The lack of an active market may also reduce the fair market value of your creditor warrants. While there are unsolicited quotes for Tidewater’s creditor warrants on the OTC Pink Market, there is no market maker for this security on the OTC Pink Market. As a result, you may find it difficult to dispose of, or to obtain accurate quotations of the price of, Tidewater’s creditor warrants. This severely limits the liquidity of Tidewater’s creditor warrants, and will likely reduce the market price of Tidewater’s creditor warrants.

There is no guarantee that the Series A Warrants and Series B Warrants issued by Tidewater in accordance with the Plan (as defined in this joint proxy statement/prospectus) will become in the money, and unexercised warrants may expire with limited or no value. Further, the terms of such warrants may be amended.

As long as Tidewater’s stock price is below the strike price of each of the Series A Warrants and Series B Warrants, ($57.06 per share for Series A Warrants, and $62.28 per share for Series B Warrants), these warrants will have limited economic value, and they may expire with limited or no value. In addition, the warrant agreement provides that the terms of the warrants may be amended without the consent of any holder to cure any ambiguity or correct any defective provision, but requires the approval by the holders of at least a certain percentage of the then-outstanding warrants originally issued to make any change that adversely affects the interests of the holders. Any material amendment to the terms of the warrant in a manner adverse to a holder would require holders of at least a certain percentage of the then-outstanding warrants, but less than all holders, approve of such amendment.

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Tidewater may not be able to maintain a listing of Tidewater common stock, Series A Warrants and Series B Warrants on the NYSE.

Tidewater must meet certain financial and liquidity criteria to maintain the listing of Tidewater’s securities on the NYSE. If Tidewater fails to meet any of the NYSE’s continued listing standards, Tidewater common stock, Series A Warrants or Series B Warrants may be delisted. A delisting of Tidewater common stock, Series A Warrants or Series B Warrants may materially impair Tidewater’s stockholders’ ability to buy and sell Tidewater common stock, Series A Warrants or Series B Warrants and could have an adverse effect on the market price of, and the efficiency of, the trading market for these securities. A delisting of Tidewater common stock, Series A Warrants or Series B Warrants could significantly impair Tidewater’s ability to raise capital.

Risks Relating to GulfMark’s Business

You should read and consider risk factors specific to GulfMark’s businesses that will also affect the combined company after the completion of the business combination. These risks are described in Part I, Item 1A of GulfMark’s Annual Report on Form 10-K for the year ended December 31, 2017, and in other documents that are incorporated by reference herein, including GulfMark’s Quarterly Report on Form 10-Q for the quarters ended March 31, 2018 and June 30, 2018. See the section entitled “Where You Can Find More Information” beginning on page 314 for the location of information incorporated by reference in this joint proxy statement/prospectus.

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COMPARATIVE PER SHARE MARKET PRICE AND DIVIDEND INFORMATION

Tidewater Market Price and Dividend Information

Tidewater common stock is listed on the NYSE under the symbol “TDW.” The following table sets forth the high and low prices per share for Tidewater common stock for the periods indicated, in each case rounded to the nearest whole cent. Tidewater’s fiscal year ends on December 31.

There were no dividends declared by Tidewater during the year ended March 31, 2017, (nor during the nine-month transition period ended December 31, 2017) and there were no dividends declared by Tidewater during the quarters ended March 31, 2018, June 30, 2018 or September 30, 2018.

You should obtain current market quotations for shares of Tidewater common stock, as the market price of Tidewater common stock will fluctuate between the date of this joint proxy statement/prospectus and the date on which the first merger is completed, at times in between and thereafter. You can obtain these quotations from publicly available sources.

Except as required under the Tidewater certificate of incorporation in order to comply with the Jones Act, during the period from July 15, 2018 until the completion of the business combination, the Tidewater Board may not, without the consent of GulfMark, declare, accrue, set aside, or pay any dividend or make any other distribution in respect of any shares of capital stock, or repurchase, redeem or reacquire capital stock or other securities, with certain exceptions set forth in the merger agreement, including (i) dividends or distributions by a direct or indirect wholly-owned subsidiary of Tidewater to Tidewater or any other direct or indirect wholly-owned subsidiary of Tidewater to the extent consistent with past practice, (ii) dividends or distributions required under the applicable organizational documents of the applicable Tidewater entity in effect on July 15, 2018, (iii) redemptions or acquisitions of securities tendered by holders of Tidewater stock-based awards in order to satisfy the obligations to pay the exercise price and/or tax withholding obligations with respect thereto, (iv) repurchase by Tidewater of its restricted stock held by an employee of Tidewater upon termination of such employee, or (v) issuances pursuant to a stockholders rights plan.

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GulfMark Market Price and Dividend Information

GulfMark common stock is listed on the NYSE MKT under the symbol “GLF.” The following table sets forth the high and low prices per share for GulfMark common stock for the periods indicated, in each case rounded to the nearest whole cent. GulfMark’s fiscal year ends on December 31.

There were no dividends declared by GulfMark during the year ended December 31, 2017, and there were no dividends declared by GulfMark during the quarters ended March 31, 2018, June 30, 2018 or September 30, 2018.

You should obtain current market quotations for shares of GulfMark common stock, as the market price of GulfMark common stock will fluctuate between the date of this joint proxy statement/prospectus and the date on which the business combination is completed, at times in between and thereafter. You can obtain these quotations from publicly available sources.

The declaration of dividends is at the discretion of the GulfMark Board. The GulfMark Board periodically reviews the GulfMark dividend policy based upon GulfMark’s financial results and cash flow projections. Decisions regarding whether or not to pay dividends and the amount of any dividends are determined after consideration of various factors, including earnings, cash requirements, the financial condition of GulfMark, the DGCL, limitations under GulfMark’s debt arrangements, the merger agreement, government regulations and other factors deemed relevant by the GulfMark Board.

Under the merger agreement, GulfMark has agreed that, until the completion of the business combination, it will not declare, set aside, make or pay any dividend or other distribution in respect of any of its capital stock.

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Comparison of Tidewater and GulfMark Market Prices and Implied Value of Share Value of the Merger Consideration

The following table sets forth the closing sale price per share of Tidewater common stock and GulfMark common stock as reported on the NYSE and NYSE MKT, respectively, on July 13, 2018, the last trading day prior to the public announcement of the merger agreement, and on October 9, 2018, the last practicable trading day before the filing of this joint proxy statement/prospectus with the SEC. The table also shows the estimated implied value of the merger consideration proposed for each share of GulfMark common stock as of the same two dates. This implied value was calculated by multiplying the closing price of a share of Tidewater common stock on the relevant date by the exchange ratio of 1.100 shares of Tidewater common stock for each share of GulfMark common stock.

The market prices of Tidewater common stock and GulfMark common stock have fluctuated since the date of the announcement of the merger agreement and will continue to fluctuate prior to, and in the case of Tidewater common stock, after, the completion of the business combination. No assurance can be given concerning the market prices of Tidewater common stock or GulfMark common stock before completion of the business combination or of Tidewater common stock after completion of the business combination. The exchange ratio is fixed in the merger agreement, but the market price of Tidewater common stock (and therefore the value of the merger consideration) when received by GulfMark stockholders after the completion of the business combination could be greater than, less than or the same as shown in the table above. Accordingly, these comparisons may not provide meaningful information to GulfMark stockholders in determining whether to approve the GulfMark merger proposal or to Tidewater stockholders in determining whether to approve the Tidewater issuance proposal. Tidewater and GulfMark stockholders are encouraged to obtain current market quotations for Tidewater common stock and GulfMark common stock and to review carefully the other information contained in this joint proxy statement/prospectus or, in the case of GulfMark, incorporated by reference herein. For more information, see the section entitled “Where You Can Find More Information” beginning on page 314 and the section entitled “Risk Factors” beginning on page 29.

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This registration statement on Form S-4, of which this joint proxy statement/prospectus forms a part, and the documents to which Tidewater and GulfMark refer you in this registration statement, of which this joint proxy statement/prospectus forms a part, as well as oral statements made or to be made by Tidewater and GulfMark, include certain “forward-looking statements” within the meaning of, and subject to the safe harbor created by, Section 27A of the Securities Act of 1933 and Section 21E of the Exchange Act (the “safe harbor provisions”). Words such as “anticipate,” “assume,” “believe,” “build,” “continue,” “create,” “design,” “estimate,” “expect,” “focus,” “forecast,” “future,” “goal,” “guidance,” “imply,” “intend,” “look,” “objective,” “opportunity,” “outlook,” “plan,” “position,” “potential,” “predict,” “project,” “prospective,” “pursue,” “seek,” “strategy,” “target,” “work,” “could,” “may,” “should,” “would,” “will” or the negative of such terms or other variations thereof, and words and terms of similar substance used in connection with any discussion of future plans, actions, or events, identify forward-looking statements with respect to the businesses, strategies and plans of Tidewater and GulfMark, their expectations relating to the business combination and their future financial condition and performance. Tidewater and GulfMark caution investors that any forward-looking statements are subject to risks and uncertainties that may cause actual results and future trends to differ materially from those matters expressed in or implied by such forward-looking statements. Investors are cautioned not to place undue reliance on forward-looking statements. Among the risks and uncertainties that could cause actual results to differ from those described in forward-looking statements are the following:

Such factors are difficult to predict and in many cases may be beyond the control of Tidewater and GulfMark. Tidewater’s and GulfMark’s forward-looking statements are based on assumptions that Tidewater and GulfMark, respectively, believe to be reasonable but that may not prove to be accurate. All of the forward-looking statements made by Tidewater or GulfMark in this joint proxy statement/prospectus are qualified by the information contained or, in the case of GulfMark, incorporated by reference herein, including the information

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contained under this heading and the information detailed in GulfMark’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017 and GulfMark’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2018. See the section entitled “Where You Can Find More Information” beginning on page 314.

Tidewater and GulfMark undertake no obligation to publicly release the result of any revisions to any such forward-looking statements that may be made to reflect events or circumstances that occur, or which they become aware of, except as required by applicable law or regulation. Readers are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof.

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INFORMATION ABOUT THE COMPANIES

Tidewater Inc.

6002 Rogerdale Road

Suite 600

Houston, Texas 77072

Phone: 713-470-5300

Tidewater Inc., a Delaware corporation that is listed on the NYSE under the symbol “TDW,” provides offshore support vessels and marine support services to the global offshore energy industry through the operation of a diversified fleet of marine service vessels. Tidewater was incorporated in 1956 and conducts its operations through wholly-owned United States (U.S.) and international subsidiaries, as well as through joint ventures in which Tidewater has either majority or occasionally non-controlling interests (generally where required to satisfy local ownership or local content requirements). Headquartered in Houston, Texas, Tidewater’s U.S. marine operations are based in Amelia, Louisiana and Houston, Texas, and Tidewater conducts international operations through facilities and offices located in over 30 countries. Tidewater has one of the broadest geographic operating footprints in the offshore energy industry with over 60 years of international experience and operations in most of the world’s significant offshore crude oil and natural gas exploration and production regions. On June 30, 2018, Tidewater owned 204 vessels (excluding 8 joint venture vessels, but including 66 stacked vessels) available to serve the global energy industry. Tidewater’s vessels and associated vessel services provide support for all phases of offshore exploration, field development and production.

GulfMark Offshore, Inc.

824 West Sam Houston Parkway North, Suite 400

Houston, Texas 77024

Phone: 713-963-9522

GulfMark, a Delaware corporation listed on the NYSE MKT under the symbol “GLF,” provides offshore marine support and transportation services primarily to companies involved in the offshore exploration and production of oil and natural gas. GulfMark’s vessels transport materials, supplies and personnel to offshore facilities, and also move and position drilling and production facilities. The majority of GulfMark’s operations are conducted in the North Sea, offshore Southeast Asia and offshore the Americas. As of August 13, 2018, GulfMark operated a fleet of 66 owned and 3 managed offshore supply vessels (“OSVs”), in the North Sea, Southeast Asia, and the Americas. GulfMark’s fleet is one of the world’s youngest, largest and most geographically balanced, high specification OSV fleets.

Gorgon Acquisition Corp.

c/o Tidewater Inc.

6002 Rogerdale Road, Suite 600

Houston, TX 77072

Phone: 713-470-5300

Merger Sub 1, with the legal name of Gorgon Acquisition Corp., will be incorporated in Delaware as a direct, wholly-owned subsidiary of Tidewater prior to the GulfMark special meeting and for the sole purpose of effecting the first merger. Upon the completion of the first merger, Merger Sub 1 will cease to exist.

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Gorgon NewCo, LLC

c/o Tidewater Inc.

6002 Rogerdale Road, Suite 600

Houston, TX 77072

Phone: 713-470-5300

Merger Sub 2, with the legal name of Gorgon NewCo, LLC, will be formed in Delaware as a direct, wholly-owned subsidiary of Tidewater simultaneously with the incorporation of Merger Sub 1 and for the sole purpose of effecting the second merger. Upon the completion of the second merger, Merger Sub 2 will survive and continue to exist as a direct, wholly owned subsidiary of Tidewater.

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SPECIAL MEETING OF TIDEWATER STOCKHOLDERS

Date, Time and Place

The Tidewater special meeting will be held at 9:00 AM Central Time on November 15, 2018 at the offices of Weil, Gotshal & Manges LLP at 700 Louisiana Street, Suite 1700, Houston, Texas 77002.

Purpose of the Tidewater Special Meeting

The purpose of the Tidewater special meeting is to:

Tidewater will transact no other business at the Tidewater special meeting.

Recommendation of the Tidewater Board

The Tidewater Board unanimously recommends that Tidewater stockholders vote:

See the section entitled “The Business Combination—Recommendation of the Tidewater Board and Reasons for the Business Combination” beginning on page 86.

Record Date

Only holders of record of issued and outstanding shares of Tidewater common stock as of the close of business on October 10, 2018, the record date for the Tidewater special meeting, are entitled to notice of, and to vote at, the Tidewater special meeting or any adjournment or postponement of the Tidewater special meeting.

Quorum; Required Votes and Broker Non-Votes

A quorum of Tidewater stockholders is necessary to hold a valid meeting. A quorum will exist at the Tidewater special meeting with respect to each matter to be considered at the Tidewater special meeting if the holders of a majority of shares of Tidewater common stock issued and outstanding and entitled to vote on the record date are present in person or represented by proxy at the Tidewater special meeting. Under the NYSE rules, brokers who hold shares in “street name” for a beneficial owner of those shares typically have the authority to vote in their discretion on “routine” proposals when they have not received instructions from beneficial owners. However, brokers are not allowed to exercise their voting discretion with respect to the approval of proposals that the NYSE determines to be “non-routine” and will not vote on such proposals if the broker has not received instructions from the beneficial owners on how to vote on the proposals. Under the NYSE rules, brokers are not permitted to vote on either of the proposals at the Tidewater special meeting. As a result, any shares held in street name will not be voted on any matter unless you affirmatively instruct your bank, broker or other nominee how to vote your shares in one of the ways indicated by your bank, broker or other nominee.

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For shares held of record, if you submit a properly executed proxy card, even if you do not vote for some or all of the proposals or vote to “ABSTAIN” in respect of some or all of the proposals, your shares of Tidewater common stock will be counted for purposes of calculating whether a quorum is present at the Tidewater special meeting with respect to each matter to be considered at the Tidewater special meeting. Executed but unvoted proxies will be voted in accordance with the recommendations of the Tidewater Board. If additional votes must be solicited to approve the Tidewater issuance proposal, it is expected that the Tidewater special meeting will be adjourned to solicit additional proxies. Shares of Tidewater common stock held in street name will be counted as present for the purpose of determining the existence of a quorum at the Tidewater special meeting so long as the beneficial owner thereof has given the bank, broker or other nominee voting instructions on at least one of the proposals brought before the Tidewater special meeting. The proposals for consideration at the Tidewater special meeting are considered “non-routine” matters under NYSE Rule 452, and, therefore, no broker has discretion to vote on any of the proposals to be considered at the meeting without voting instructions from the beneficial owner of the shares. A stockholder’s shares will not be counted as present for the purpose of determining the existence of a quorum if no instructions have been provided on how to vote on any of the proposals.

Approval of the Tidewater issuance proposal requires the affirmative vote of a majority of the voting power present in person or by proxy at the Tidewater special meeting and entitled to vote on the proposal. With respect to the Tidewater issuance proposal, you may vote “FOR,” “AGAINST” or “ABSTAIN.” If you “abstain” from voting with respect to this proposal, your vote will the same effect as a vote “AGAINST” this proposal. Broker non-votes and shares held by Tidewater stockholders that neither are in attendance at, nor have submitted a proxy for, the Tidewater special meeting will have no effect on the outcome of any vote to approve the Tidewater issuance proposal.

Approval of the Tidewater adjournment proposal requires the affirmative vote of a majority of the voting power present in person or by proxy at the Tidewater special meeting and entitled to vote on the proposal. With respect to the Tidewater adjournment proposal, you may vote “FOR,” “AGAINST” or “ABSTAIN.” If you “abstain” from voting with respect to this proposal, your vote will have the same effect as a vote “AGAINST” the proposal. Broker non-votes and shares held by Tidewater stockholders that neither are in attendance at, nor have submitted a proxy for, the Tidewater special meeting will have no effect on the outcome of any vote on the Tidewater adjournment proposal.

The matters to be voted on at the Tidewater special meeting are described in the section entitled “Tidewater Proposals” beginning on page 65.

Methods of Voting

If your shares of Tidewater common stock are registered in your name with Tidewater’s transfer agent, Computershare, you are a stockholder of record with respect to those shares and you received printed proxy materials directly from us. If your shares are held in an account at a bank, broker or other nominee, you are the “beneficial owner” of such shares and the printed proxy materials were forwarded to you by that bank, broker or other nominee. In that circumstance, the bank, broker or other nominee is considered the stockholder of record for purposes of voting at the Tidewater special meeting. As a beneficial owner, you have the right to instruct the bank, broker or other nominee how to vote the shares held in your account.

If you are a stockholder of record of Tidewater common stock, you may vote:

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If you are a beneficial owner of shares of Tidewater common stock held in street name, you may submit voting instructions to your bank, broker or other nominee:

We provide Internet proxy voting to allow you to vote your shares online. However, please be aware you must bear any costs associated with your Internet access, such as usage charges from Internet access providers or telecommunication companies.

Voting in Person

Owners of record will need to have a valid form of government-issued photo identification to be admitted to the Tidewater special meeting. If your ownership is through a bank, broker or other nominee, then, in addition to a valid form of government-issued photo identification, you will also need to have proof of your share ownership to be admitted to the Tidewater special meeting. A recent account statement, letter or proxy from your bank, broker or other nominee will suffice. In order to vote at the Tidewater special meeting, if you are not an owner of record, you must first obtain a legal proxy form from the bank, broker or other nominee that holds your shares. Even if you plan to attend the Tidewater special meeting, the Tidewater Board recommends that you vote your shares in advance as described below so that your vote will be counted if you later decide not to attend the Tidewater special meeting.

Voting by Proxy

If you hold your shares directly as the stockholder of record, you may vote by proxy without attending the Tidewater special meeting. You can vote by proxy via the Internet, by telephone or by mail by following the instructions provided in the enclosed proxy card. If you are the beneficial owner of shares held in street name, you should follow the instructions provided on the voting instructions form provided by your bank, broker or other nominee.

Contact Information for Questions About Voting

If you have any questions about how to vote or direct a vote in respect of your shares of Tidewater common stock, you may contact MacKenzie Partners, Tidewater’s proxy solicitor, at:

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Revocability of Proxies

If you are a stockholder of record of Tidewater, you may change your vote or revoke your proxy at any time before your shares are voted at the Tidewater special meeting by:

If you are a beneficial owner of shares of Tidewater common stock, you must contact your bank, broker or other nominee with whom you have an account to obtain information regarding changing your voting instructions.

Proxy Solicitation Costs

The enclosed proxy card is being solicited on behalf of the Tidewater Board. In addition to solicitation by mail, Tidewater’s directors, officers and employees may solicit proxies in person, by telephone or by electronic means. These persons will not be specifically compensated for doing this.

Tidewater has retained MacKenzie Partners to assist in the solicitation process. Tidewater will pay MacKenzie Partners a fee of approximately $20,000 as well as reasonable and documented out-of-pocket expenses. Tidewater also has agreed to indemnify MacKenzie Partners against various liabilities and expenses that relate to or arise out of its solicitation of proxies (subject to certain exceptions).

Tidewater will ask banks, brokers and other custodians, nominees and fiduciaries to forward the proxy solicitation materials to the beneficial owners of shares of Tidewater common stock held of record by such nominee holders. Tidewater will reimburse these nominee holders for their customary clerical and mailing expenses incurred in forwarding the proxy solicitation materials to the beneficial owners.

No Appraisal Rights

Under Delaware law, Tidewater stockholders are not entitled to appraisal rights in connection with the Tidewater issuance proposal.

Other Information

The matters to be considered at the Tidewater special meeting are of great importance to the Tidewater stockholders. Accordingly, you are urged to read and carefully consider the information contained in this joint proxy statement/prospectus and submit your proxy via the Internet or by telephone or complete, date, sign and promptly return the enclosed proxy card in the enclosed postage-paid envelope. If you submit your proxy via the Internet or by telephone, you do not need to return the enclosed proxy card.

Vote of Tidewater’s Directors and Executive Officers

As of October 9, 2018, Tidewater directors and executive officers, and their affiliates, as a group, owned and were entitled to vote 150,317 shares of Tidewater common stock, or less than 1% of the total outstanding shares of Tidewater common stock. This figure does not include an aggregate 13,376 Tidewater equity warrants held by such persons, which are immediately exercisable on a one-for-one basis.

Tidewater currently expects that all of its directors and executive officers will vote their shares “FOR” the Tidewater issuance proposal and “FOR” the Tidewater adjournment proposal.

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Attending the Tidewater Special Meeting

You are entitled to attend the Tidewater special meeting only if you were a stockholder of record of Tidewater at the close of business on the record date or you are the beneficial owner of shares of Tidewater held in the name of a bank, broker or other nominee as of the record date, or you hold a valid proxy for the Tidewater special meeting.

If you were a stockholder of record of Tidewater at the close of business on the record date and wish to attend the Tidewater special meeting, please so indicate on the appropriate proxy card or as prompted by the Internet or telephone voting system. Your name will be verified against the list of stockholders of record prior to your being admitted to the Tidewater special meeting.

If a bank, broker or other nominee is the record owner of your shares of Tidewater common stock, you will need to have proof that you are the beneficial owner as of the record date to be admitted to the Tidewater special meeting. A recent statement or letter from your bank, broker or other nominee confirming your ownership as of the record date, or presentation of a valid proxy from a bank, broker or other nominee that is the record owner of your shares, would be acceptable proof of your beneficial ownership.

You should be prepared to present government-issued photo identification for admittance to the Tidewater special meeting. If you do not provide government-issued photo identification or comply with the other procedures outlined above upon request, you might not be admitted to the Tidewater special meeting.

Results of the Tidewater Special Meeting

Within four business days following the Tidewater special meeting, Tidewater intends to file the final voting results with the SEC on a Current Report on Form 8-K. If the final voting results have not been certified within that four business day period, Tidewater will report the preliminary voting results on a Current Report on Form 8-K at that time and will file an amendment to the Current Report on Form 8-K to report the final voting results within four business days of the date that the final results are certified.

TIDEWATER STOCKHOLDERS SHOULD CAREFULLY READ THIS JOINT PROXY STATEMENT/PROSPECTUS IN ITS ENTIRETY FOR MORE DETAILED INFORMATION CONCERNING THE TIDEWATER ISSUANCE PROPOSAL AND THE TIDEWATER ADJOURNMENT PROPOSAL.

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TIDEWATER PROPOSALS

Tidewater Issuance Proposal

It is a condition to completion of the business combination that Tidewater stockholders approve the Tidewater issuance proposal. In the business combination, each GulfMark stockholder will receive, for each share of GulfMark common stock that is issued and outstanding immediately prior to the effective time of the first merger, 1.100 shares of Tidewater common stock and each GulfMark warrant that is outstanding will be converted automatically into a warrant representing a right to acquire Tidewater shares of common stock, on substantially the same terms and conditions as applied to such GulfMark warrant immediately prior to the effective time of the first merger, but subject to the limitations set forth in the Tidewater certificate of incorporation in order to comply with the Jones Act, except that the number of shares of Tidewater common stock subject to such GulfMark warrant will be adjusted to reflect the exchange ratio as provided in the merger agreement. In addition, each GulfMark RSU will, automatically and without any action on the part of the holder thereof, cease to represent an award denominated in GulfMark common stock and be converted into a substantially similar award for, or with respect to, Tidewater common stock, and the number of shares of Tidewater common stock subject to each such award will be equal to the product of the number of shares of GulfMark common stock subject to such GulfMark RSU immediately prior to the effective time of the first merger multiplied by the exchange ratio, rounded down to the nearest whole number. See “The Merger Agreement—Merger Consideration” beginning on page 126.

Under the NYSE rules, a company is required to obtain stockholder approval prior to the issuance of common stock if the number of shares of common stock to be issued is, or will be upon issuance, equal to or in excess of 20% of the number of shares of common stock outstanding before the issuance of the common stock. If the business combination is completed pursuant to the merger agreement, Tidewater expects to issue up to approximately 11,987,730 shares of Tidewater common stock in connection with the first merger, depending upon the number of shares of GulfMark common stock (other than excluded shares) outstanding as of the effective time of the first merger. Accordingly, the aggregate number of shares of Tidewater common stock that Tidewater will issue in the first merger will exceed 20% of the shares of Tidewater common stock issued and outstanding before such issuance. For this reason, Tidewater is seeking the approval of Tidewater stockholders for the Tidewater issuance proposal. In the event the Tidewater issuance proposal is not approved by Tidewater stockholders, the business combination cannot be completed.

In the event the Tidewater issuance proposal is approved by Tidewater stockholders, but the merger agreement is terminated without the business combination being completed, Tidewater will not issue any shares of Tidewater common stock despite the approval of the Tidewater issuance proposal.

Approval of the Tidewater issuance proposal requires the affirmative vote of a majority of the voting power present in person or by proxy at the Tidewater special meeting and entitled to vote on the proposal. If you “abstain” from voting with respect to this proposal, your vote will the same effect as a vote “AGAINST” this proposal. Broker non-votes and shares held by Tidewater stockholders that neither are in attendance at, nor have submitted a proxy for, the Tidewater special meeting will have no effect on the outcome of any vote to approve the Tidewater issuance proposal.

The Tidewater Board unanimously recommends you vote “FOR” the Tidewater issuance proposal.

Tidewater Adjournment Proposal

Tidewater stockholders are also being asked to approve the Tidewater adjournment proposal. Approval of the Tidewater adjournment proposal requires the affirmative vote of the majority of the voting power present in person or by proxy at the Tidewater special meeting and entitled to vote on the proposal. If you “abstain” from voting with respect to this proposal, your vote will have the same effect as a vote “AGAINST” the proposal. Broker non-votes and shares held by Tidewater stockholders that neither are in attendance at, nor have

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submitted a proxy for, the Tidewater special meeting will have no effect on the outcome of any vote on the Tidewater adjournment proposal.

If the Tidewater special meeting is adjourned for the purpose of soliciting additional proxies, stockholders who have already submitted revocable proxies will be able to revoke them at any time prior to their exercise.

Approval of the Tidewater adjournment proposal is not required in order for the Tidewater special meeting to be adjourned. Under the Tidewater bylaws, the presiding person of the Tidewater special meeting has the power to adjourn or recess the Tidewater special meeting from time to time whether or not a quorum is present.

The Tidewater Board unanimously recommends you vote “FOR” the Tidewater adjournment proposal.

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SPECIAL MEETING OF GULFMARK STOCKHOLDERS

Date, Time and Place

The GulfMark special meeting will be held on November 15, 2018 at 9:00 AM Eastern Time at the offices of Gibson, Dunn & Crutcher LLP at 200 Park Avenue, New York, New York 10166.

Purpose of the GulfMark Special Meeting

The purpose of the GulfMark special meeting is as follows:

GulfMark will transact no other business at the GulfMark special meeting.

Recommendation of the GulfMark Board of Directors

The GulfMark Board unanimously recommends that GulfMark stockholders vote:

See section entitled “The Business Combination—Recommendation of the GulfMark Board and Reasons for the Business Combination” beginning on page 101.

Record Date

Only holders of record of issued and outstanding shares of GulfMark common stock as of the close of business on October 12, 2018 the record date for the GulfMark special meeting, are entitled to notice of, and to vote at, the GulfMark special meeting or any adjournment or postponement of the GulfMark special meeting.

Quorum; Required Votes; Abstentions and Broker Non-Votes

A quorum of GulfMark stockholders is necessary to hold a valid meeting. A quorum will exist at the GulfMark special meeting with respect to each matter to be considered at the GulfMark special meeting if the holders of a majority of shares of GulfMark common stock issued and outstanding and entitled to vote on the record date are present in person or represented by proxy at the GulfMark special meeting. All shares represented by proxy are counted as present for purposes of establishing a quorum, including abstentions. Under the NYSE rules, brokers who hold shares in “street name” for a beneficial owner of those shares typically have the authority to vote in their discretion on “routine” proposals when they have not received instructions from beneficial owners. However, brokers are not allowed to exercise their voting discretion with respect to the approval of proposals that the NYSE determines to be “non-routine” and will not vote on such proposals if the broker has not received

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instructions from the beneficial owners on how to vote on the proposals. Under the NYSE rules, brokers are not permitted to vote on any of the matters to be considered at the GulfMark special meeting. As a result, your shares will not be voted on any matter unless you affirmatively instruct your bank, broker or other nominee how to vote your shares in one of the ways indicated by your bank, broker or other nominee.

If you submit a properly executed proxy card, even if you do not vote for some or all of the proposals or vote to “ABSTAIN” in respect of some or all of the proposals, your shares of GulfMark common stock will be counted for purposes of calculating whether a quorum is present at the GulfMark special meeting with respect to each matter to be considered at the GulfMark special meeting. Executed but unvoted proxies will be voted in accordance with the recommendations of the GulfMark Board. If additional votes must be solicited to approve the GulfMark merger proposal, it is expected that the meeting will be adjourned to solicit additional proxies. Shares of GulfMark common stock held in street name will be counted as present for the purpose of determining the existence of a quorum at the GulfMark special meeting so long as a stockholder has given the broker or other nominee voting instructions on at least one of the proposals brought before the GulfMark special meeting. The proposals for consideration at the GulfMark special meeting are considered “non-routine” matters, and, therefore, no broker has discretion to vote on any of the proposals to be considered at the meeting without voting instructions from the beneficial owner of the shares. A stockholder’s shares will not be counted as present for the purpose of determining the existence of a quorum if no instructions have been provided on how to vote on any such proposals.

Approval of the GulfMark merger proposal requires the affirmative vote of a majority of the shares of GulfMark common stock outstanding as of the close of business on the record date and entitled to vote on the proposal. Failures to vote, votes to abstain, and broker non-votes will have the same effect as a vote “AGAINST” the GulfMark merger proposal.

Approval of the GulfMark compensation proposal requires the affirmative vote of a majority of the shares of GulfMark common stock present in person or by proxy at the GulfMark special meeting and entitled to vote on the proposal. Broker non-votes and shares held by GulfMark stockholders who neither are in attendance at, nor have submitted a proxy for, the GulfMark special meeting will have no effect on the outcome of any vote to approve the GulfMark compensation proposal. Votes to abstain will have the same effect as a vote “AGAINST” the GulfMark compensation proposal.

Approval of the GulfMark adjournment proposal requires the affirmative vote of a majority of the shares of GulfMark common stock present in person or by proxy at the GulfMark special meeting and entitled to vote on the proposal. Broker non-votes and shares held by GulfMark stockholders who neither are in attendance at, nor have submitted a proxy for, the GulfMark special meeting will have no effect on the outcome of any vote to approve the GulfMark adjournment proposal. Votes to abstain will have the same effect as a vote “AGAINST” the GulfMark adjournment proposal.

The matters to be voted on at the GulfMark special meeting are described in the section entitled “GulfMark Proposals” beginning on page 72.

Methods of Voting

GulfMark stockholders holding shares directly as stockholders of record may vote via the Internet by going to the web address provided on the enclosed proxy card and following the instructions for Internet voting; by telephone using the toll-free telephone number listed on the enclosed proxy card; or by completing, signing, dating and returning the enclosed proxy card in the postage-paid envelope provided.

GulfMark stockholders of record may vote their shares in person by ballot at the GulfMark special meeting or by submitting their proxies:

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Stockholders of GulfMark whose shares are held in “street name” by a broker, nominee, fiduciary or other custodian should refer to the proxy card, voting instruction form or other information forwarded by their broker, nominee, fiduciary or other custodian for instructions on how to vote their shares.

Voting in Person

Shares held directly in your name as stockholder of record may be voted in person at the GulfMark special meeting. If you choose to vote your shares in person at the GulfMark special meeting, please bring your enclosed proxy card and proper identification, such as a driver’s license. Even if you plan to attend the GulfMark special meeting, the GulfMark Board recommends that you vote your shares in advance as described below so that your vote will be counted if you later decide not to attend the GulfMark special meeting.

If you are a beneficial holder of your shares of GulfMark stock, you will receive separate voting instructions from your broker, bank or other nominee explaining how to vote your shares. Please note that if your shares are held in “street name” by a broker, bank or other nominee and you wish to vote at the GulfMark special meeting, you will not be permitted to vote in person unless you first obtain a legal proxy issued in your name from the record owner. You are encouraged to request a legal proxy from your broker, bank or other nominee promptly as the process can be lengthy.

Voting by Proxy

If you hold your shares of GulfMark common stock directly as the stockholder of record you may direct your vote by proxy without attending the GulfMark special meeting. You can vote by proxy via the Internet, by telephone or by mail by following the instructions provided in the enclosed proxy card.

Stockholders of GulfMark whose shares are held in “street name” by a broker, nominee, fiduciary or other custodian should refer to the proxy card, voting instruction form or other information forwarded by their broker, nominee, fiduciary or other custodian for instructions on how to vote their shares.

Contact Information for Questions About Voting

If you have any questions about how to vote or direct a vote in respect of your shares of GulfMark common stock, you may contact Innisfree, GulfMark’s proxy solicitor, at:

Revocability of Proxies

If you are a stockholder of record of GulfMark, whether you vote via the Internet, by telephone or mail, you can change or revoke your proxy before it is voted at the GulfMark special meeting in one of the following ways:

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Proxy Solicitation Costs

The enclosed proxy card is being solicited on behalf of the GulfMark Board. In addition to solicitation by mail, GulfMark’s directors, officers and employees may solicit proxies in person, by telephone or by electronic means. These persons will not be specifically compensated for doing this.

GulfMark has retained Innisfree to assist in the solicitation process. GulfMark will pay Innisfree a fee of approximately $30,000, as well as reasonable and documented out-of-pocket expenses. GulfMark also has agreed to indemnify Innisfree against various liabilities and expenses that relate to or arise out of its solicitation of proxies (subject to certain exceptions).

GulfMark will ask banks, brokers and other custodians, nominees and fiduciaries to forward the proxy solicitation materials to the beneficial owners of shares of GulfMark common stock held of record by such nominee holders. GulfMark will reimburse these nominee holders for their customary clerical and mailing expenses incurred in forwarding the proxy solicitation materials to the beneficial owners.

No Appraisal Rights

Under Delaware law, GulfMark stockholders are not entitled to appraisal rights in connection with the mergers.

Other Information

The matters to be considered at the GulfMark special meeting are of great importance to GulfMark stockholders. Accordingly, you are urged to read and carefully consider the information contained in or incorporated by reference into this joint proxy statement/prospectus and submit your proxy via the Internet or by telephone or complete, date, sign and promptly return the enclosed proxy card in the enclosed postage-paid envelope. If you submit your proxy via the Internet or by telephone, you do not need to return the enclosed proxy card.

Vote of GulfMark’s Directors and Executive Officers

As of October 9, 2018, GulfMark directors and executive officers, and their affiliates (excluding Raging and Captain Q), as a group, were entitled to vote or had shared power to vote a total of 1,194 shares of GulfMark common stock, or less than 1% of the total shares of GulfMark common stock issued and outstanding as of October 9, 2018. For more information, see the section entitled “Voting and Support Agreements” beginning on page 156.

GulfMark currently expects that all of its directors and executive officers will vote their shares “FOR” the GulfMark merger proposal, “FOR” the GulfMark compensation proposal and “FOR” the GulfMark adjournment proposal.

Attending the GulfMark Special Meeting

You are entitled to attend the GulfMark special meeting only if you were a stockholder of record of GulfMark at the close of business on the record date or you held your shares of GulfMark beneficially in the name of a broker, bank or other nominee as of the record date or you hold a valid proxy for the GulfMark special meeting.

If you were a stockholder of record of GulfMark at the close of business on the record date and wish to attend the GulfMark special meeting, please so indicate on the appropriate proxy card or as prompted by the Internet or telephone voting system. Your name will be verified against the list of GulfMark stockholders of record prior to your being admitted to the GulfMark special meeting.

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If a broker, bank or other nominee is the record owner of your shares of GulfMark common stock, you will need to have proof that you are the beneficial owner as of the record date to be admitted to the GulfMark special meeting. A recent statement or letter from your broker, bank or other nominee confirming your ownership as of the record date, or presentation of a valid proxy from a broker, bank or other nominee that is the record owner of your shares, would be acceptable proof of your beneficial ownership.

You should be prepared to present proper identification, such as a driver’s license, for admittance to the GulfMark special meeting. If you do not provide government-issued photo identification or comply with the other procedures outlined above upon request, you might not be admitted to the GulfMark special meeting.

Results of the GulfMark Special Meeting

Within four business days following the GulfMark special meeting, GulfMark intends to file the final voting results with the SEC on a Current Report on Form 8-K. If the final voting results have not been certified within that four business day period, GulfMark will report the preliminary voting results on a Current Report on Form 8-K at that time and will file an amendment to the Current Report on Form 8-K to report the final voting results within four business days of the date that the final results are certified.

GULFMARK STOCKHOLDERS SHOULD CAREFULLY READ THIS JOINT PROXY STATEMENT/PROSPECTUS IN ITS ENTIRETY FOR MORE DETAILED INFORMATION CONCERNING THE GULFMARK MERGER PROPOSAL AND THE OTHER MATTERS TO BE VOTED ON AT THE GULFMARK SPECIAL MEETING.

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GULFMARK PROPOSALS

Merger Proposal

It is a condition to the completion of the business combination that GulfMark stockholders adopt the merger agreement. In the business combination, each GulfMark stockholder will receive, for each share of GulfMark common stock that is issued and outstanding as of immediately prior to the effective time of the first merger, 1.100 shares of Tidewater common stock. Each outstanding GulfMark warrant will be converted automatically into a warrant representing a right to acquire shares of Tidewater common stock, on substantially the same terms and conditions as applied to such GulfMark warrant immediately prior to the effective time of the first merger, but subject to the limitations set forth in the Tidewater certificate of incorporation in order to comply with the Jones Act, except that the number of shares of Tidewater common stock subject to such GulfMark warrant will be adjusted to reflect the exchange ratio as provided in the merger agreement. In addition, each outstanding restricted stock unit, which are referred to as the GulfMark RSUs, representing the right to vest in and be issued shares of GulfMark common stock by GulfMark, will, automatically and without any action on the part of the holder thereof, cease to represent an award denominated in GulfMark common stock and be converted into a substantially similar award for, or with respect to, Tidewater common stock, and the number of shares of Tidewater common stock subject to each such award will be equal to the product of the number of shares of GulfMark common stock subject to such GulfMark RSU immediately prior to the effective time of the first merger multiplied by the exchange ratio, rounded down to the nearest whole number.

The approval by the GulfMark stockholders of this proposal is required by Section 251(c) of the DGCL and is a condition to the completion of the business combination.

Approval of the GulfMark merger proposal requires the affirmative vote of a majority of the shares of GulfMark common stock outstanding as of the close of business on the record date and entitled to vote. Failures to vote, votes to abstain, and broker non-votes will have the same effect as a vote “AGAINST” the GulfMark merger proposal.

The GulfMark Board unanimously recommends that you vote “FOR” the GulfMark merger proposal.

GulfMark Compensation Proposal

As required by Section 14A of the Exchange Act and the applicable SEC rules issued thereunder, GulfMark is providing its stockholders the opportunity to vote to approve, on a non-binding, advisory basis, certain compensation that may be paid or become payable to GulfMark’s named executive officers that is based on or otherwise relates to the business combination, as described in the section entitled “The Business Combination—Interests of GulfMark Directors and Executive Officers in the Business Combination” beginning on page 118. Accordingly, GulfMark stockholders are being provided the opportunity to cast an advisory vote on such potential payments.

As an advisory vote, this proposal is not binding upon GulfMark or the GulfMark Board and approval of this proposal is not a condition to the completion of the business combination. Because the business combination-related executive compensation to be paid in connection with the business combination is based on the terms of the merger agreement as well as the contractual arrangements with GulfMark’s named executive officers, such compensation will be payable, regardless of the outcome of this advisory vote, if the merger agreement is adopted (subject only to the contractual conditions applicable thereto). However, GulfMark seeks the support of its stockholders and believes that stockholder support is appropriate because GulfMark has a comprehensive executive compensation program designed to link the compensation of its executives with GulfMark’s performance and the interests of GulfMark stockholders.

Approval of the GulfMark compensation proposal requires the affirmative vote of a majority of the shares of GulfMark common stock present in person or by proxy at the GulfMark special meeting and entitled to vote on

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the proposal. Broker non-votes and shares held by GulfMark stockholders who neither are in attendance at, nor have submitted a proxy for, the GulfMark special meeting will have no effect on the outcome of any vote to approve the GulfMark compensation proposal. Votes to abstain will have the same effect as a vote “AGAINST” the GulfMark compensation proposal.

The GulfMark Board unanimously recommends that you vote “FOR” the GulfMark compensation proposal.

GulfMark Adjournment Proposal

GulfMark stockholders are also being asked to approve a proposal to adjourn the GulfMark special meeting, if reasonably necessary to provide stockholders with any required supplement or amendment to the joint proxy statement/prospectus or to solicit additional proxies in favor of the GulfMark merger proposal in the event there are not sufficient votes at the time of the GulfMark special meeting to approve the GulfMark merger proposal. If the GulfMark special meeting is adjourned for the purpose of soliciting additional proxies, stockholders who have already submitted revocable proxies will be able to revoke them at any time prior to their exercise.

Approval of the GulfMark adjournment proposal requires the affirmative vote of a majority of the shares of GulfMark common stock present in person or by proxy at the GulfMark special meeting and entitled to vote on the proposal. Broker non-votes and shares held by GulfMark stockholders who neither are in attendance at, nor have submitted a proxy for, the GulfMark special meeting will have no effect on the outcome of any vote to approve the GulfMark adjournment proposal. Votes to abstain will have the same effect as a vote “AGAINST” the GulfMark adjournment proposal.

The GulfMark Board unanimously recommends that you vote “FOR” the GulfMark adjournment proposal.

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THE BUSINESS COMBINATION

This discussion of the business combination, is qualified in its entirety by reference to the merger agreement, which is attached to this joint proxy statement/prospectus as Annex A and incorporated by reference herein in its entirety. You should read the entire merger agreement carefully as it is the legal document that governs the business combination.

Transaction Structure

At the effective time of the first merger, Merger Sub 1 will merge with and into GulfMark. As a result of the first merger, the separate corporate existence of Merger Sub 1 will cease, and GulfMark will continue as the surviving corporation and as a wholly owned subsidiary of Tidewater.

Immediately following the completion of the first merger, GulfMark will merge with and into Merger Sub 2. As a result of the second merger, the separate corporate existence of GulfMark will cease, and Merger Sub 2 will continue as the surviving company and as a wholly owned subsidiary of Tidewater.

The mergers are intended to qualify together as a “reorganization” within the meaning of Section 368(a) of the Code.

Consideration to GulfMark Stockholders

As a result of the first merger, each share of GulfMark common stock issued and outstanding immediately prior to the first merger (other than excluded shares, as defined below) will be converted into the right to receive 1.100 shares of Tidewater common stock.

Shares held by GulfMark, Tidewater or any of Tidewater’s direct or indirect subsidiaries as of the effective time of the first merger (the “excluded shares”), will be cancelled and will cease to exist, and no consideration will be delivered in exchange therefor.

No fractional shares of Tidewater common stock will be issued in the first merger. Instead, each GulfMark stockholder who would otherwise be entitled to receive a fraction of a share of Tidewater common stock (after aggregating all fractional shares of Tidewater common stock issuable to such stockholder) will be entitled to receive, in lieu of such fractional shares, a dollar amount in cash (rounded up to the nearest whole cent), without interest, equal to the product of the average of the closing prices per share of Tidewater common stock traded on the NYSE for the 10 full trading days ending on the day immediately preceding the date on which the effective time occurs multiplied by the fraction of shares of Tidewater stock to which such stockholder would otherwise be entitled.

Background of the Business Combination

Tidewater and GulfMark both own and operate large fleets of offshore support vessels globally, providing marine transportation services to the energy industry worldwide. The global OSV industry is a highly fragmented industry. Both companies share the view that there is a significant opportunity for consolidation to improve efficiencies through additional scale. As a part of their efforts to strengthen their respective businesses and enhance stockholder value, the boards of directors and senior management of each of Tidewater and GulfMark regularly review and assess their respective companies’ operations, performance, prospects and the strategic landscape in the industry, including the possibility of pursuing various strategic transactions. From time to time, the senior management of Tidewater and GulfMark have held conversations and communicated with various investment banking firms regarding potential strategic transaction opportunities and other strategic alternatives available to each of them.

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In May 2017, in response to the significant and sustained decline in commodity prices and resulting decline in the utilization of their respective offshore support vessels, as well as the decline in average day rates received and vessel revenue, both Tidewater and GulfMark separately filed for Chapter 11 bankruptcy.

On July 31, 2017, Tidewater emerged from bankruptcy.

On September 14, 2017, at the direction of the then Chief Executive Officer of Tidewater, Mr. Jeffrey Platt, and the Chairman of the Tidewater Board, Mr. Thomas Bates, a representative of Lazard Frères & Co. LLC, Tidewater’s financial advisor on potential strategic transactions (“Lazard”), contacted a representative of the financial advisor to the committee of creditors in the GulfMark Chapter 11 proceedings to communicate Tidewater’s interest in discussing the possibility of a potential combination of the two companies. The financial advisor to the committee of creditors in the GulfMark Chapter 11 proceedings indicated to the Lazard representative that any conversation regarding a potential business combination should wait until after GulfMark’s emergence from bankruptcy proceedings. Lazard reported the outcome of that conversation to Mr. Platt and Mr. Quinn Fanning, Tidewater’s Chief Financial Officer, on September 19, 2017.

On October 15, 2017, Mr. Platt retired as Chief Executive Officer of Tidewater, and Mr. Larry Rigdon, a member of the Tidewater Board, was appointed Interim Chief Executive Officer on October 16, 2017.

On November 14, 2017, GulfMark emerged from bankruptcy.

On December 5, 2017, Mr. Ken Traub, a member of the GulfMark Board, and Mr. Bill Martin, a former member of the GulfMark Board, met with Mr. Bates at Mr. Bates’ request. At the meeting, among other things, Mr. Bates discussed his views regarding Tidewater and potential industry consolidation. Mr. Traub then reported the meeting to the rest of the GulfMark Board.

On December 7, 2017, the GulfMark Board met in Houston, Texas to discuss, among other things, current industry dynamics, a review of the GulfMark fleet and potential vessel divestitures and potential strategic transactions, including potential business combinations.

On December 20, 2017, Mr. Scott McCarty, a member of the GulfMark Board, sent an introductory email to Messrs. Bates and Louis Raspino, Chairman of the GulfMark Board. Mr. Bates responded to that email requesting that he and Mr. Raspino discuss exploring a potential transaction between the companies in the new year.

On January 4, 2018, a representative of a third-party industry participant, referred to herein as Party X, reached out to Mr. McCarty to arrange a meeting with such meeting to occur later in the month. Mr. McCarty then reported the call to the rest of the GulfMark Board.

On January 10, 2018, at a meeting of the GulfMark Board in Houston, Texas, the GulfMark Board discussed several investment banks as potential financial advisors for a strategic transaction, including Evercore, with a view toward retaining a financial advisor to assist the GulfMark Board and management in evaluating a broad range of strategic alternatives available to GulfMark. Evercore had acted as financial advisor to GulfMark in connection with its bankruptcy filing. Evercore’s engagement terminated in November 2017, shortly after GulfMark emerged from bankruptcy.

On January 15, 2018, Lazard was formally engaged by Tidewater to act as financial advisor in connection with a potential transaction with GulfMark. The Tidewater Board determined to engage Lazard due to its familiarity with Tidewater and GulfMark as well as its expertise in transactions similar to the potential transaction with GulfMark. Mr. Rigdon contacted Lazard and requested that Lazard be prepared to share its views with the Tidewater Board regarding a potential strategic combination with GulfMark.

On January 22, 2018, Mr. Bates met with Mr. McCarty in Fort Worth, Texas. During that meeting, they discussed the possibility of exploring a potential strategic combination between Tidewater and GulfMark, including potential cost synergies and other potential benefits for the stockholders of both companies.

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On January 24, 2018, Messrs. Bates, Rigdon and Raspino met in person in Houston, Texas. During this meeting, Messrs. Bates, Rigdon and Raspino further discussed the possibility of exploring a potential strategic transaction between Tidewater and GulfMark.

On January 26, 2018, representatives of Party X met with Mr. McCarty and Mr. Traub in New York City to discuss a potential business combination between Party X and GulfMark. Subsequently, the participants at the meeting updated the GulfMark Board regarding the discussion. Representatives of Party X then delivered a draft mutual confidentiality agreement to GulfMark to facilitate the exchange of confidential information between Party X and GulfMark. Also on January 26, 2018, the Chief Executive Officer of Party X sent Mr. Quintin Kneen, Director, President and Chief Executive Officer of GulfMark, a request for a meeting.

On January 30, 2018, the Tidewater Board held a telephonic meeting. During this meeting, the Tidewater Board discussed various strategic opportunities that could be available to Tidewater, including a potential transaction with GulfMark and other potential acquisition opportunities. Mr. Bates updated the Tidewater Board on the conversations among himself, Mr. Rigdon and Mr. Raspino concerning a potential strategic transaction between Tidewater and GulfMark. Mr. Rigdon further advised the Tidewater Board that he had contacted Lazard to review with the Tidewater Board its views based on publicly available information concerning a potential transaction with GulfMark. Representatives of Lazard discussed its views with the Tidewater Board regarding a potential combination with GulfMark. Following this discussion, the Tidewater Board authorized Tidewater management to prepare a written indication of interest letter to be delivered to GulfMark contemplating a stock-for-stock combination between the two companies.

On January 31, 2018, Mr. Kneen and the Chief Executive Officer of Party X met in Houston, Texas, at which time they discussed, among other things, a potential business combination between Party X and GulfMark.

On January 31, 2018, Tidewater engaged Weil, Gotshal & Manges LLP (“Weil”) as its mergers and acquisitions legal counsel in connection with the potential transaction involving GulfMark. The Tidewater Board determined to engage Weil due to its expertise in transactions similar to the potential transaction with GulfMark.

On February 2, 2018, Mr. Rigdon delivered to Mr. Raspino a written indication of interest letter contemplating a stock-for-stock combination between the two companies. In the letter, Tidewater noted that, based on its preliminary views and using external projections for GulfMark on a “like-for-like” basis, Tidewater anticipated that upon completion of the transaction, GulfMark stockholders would own approximately 25% of the equity of the combined company. Such ownership level equated to an approximately “at market” exchange ratio given Tidewater’s and GulfMark’s stock prices at the time.

On February 5, 2018, the GulfMark Board held a telephonic meeting, together with representatives of Evercore, to discuss the letter received by Mr. Raspino on February 2, 2018, as well as the January 24, 2018 meeting between Messrs. Raspino, Rigdon, and Bates. Representatives of Evercore reviewed with the GulfMark Board publicly available information regarding Tidewater and its fleet and financial information, and the directors and representatives of Evercore discussed certain considerations in a potential transaction with Tidewater, including a pro forma fleet overview and preliminary financial considerations.

On February 7, 2018, Mr. Kneen met with the Chief Executive Officer of Party X at which time the Chief Executive Officer of Party X requested that representatives of the large stockholders of GulfMark attend a meeting with representatives of Party X.

On February 9, 2018, GulfMark engaged Gibson, Dunn & Crutcher LLP (“Gibson”) as its legal counsel in connection with the receipt of the letter from Tidewater and a potential business combination transaction. GulfMark determined to engage Gibson due to its expertise in transactions similar to the potential transaction with Tidewater.

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On February 17, 2018, the GulfMark Board held a telephonic meeting to continue discussions regarding the proposal from Tidewater and the requested meeting with Party X. Representatives of Gibson were present and discussed with the GulfMark Board, among other things, the fiduciary duties of the GulfMark Board in connection with responding to the Tidewater proposal. In addition, directors and representatives of Evercore discussed potential strategic alternatives, including other potential transactions and continuing as a standalone company. At the conclusion of such meeting, the GulfMark Board supported further exploration of the merits of a potential transaction with Tidewater, including the exchange of confidential information with Tidewater. The GulfMark Board instructed the representatives of Evercore to contact representatives of Lazard to express interest in further exploring a potential transaction with Tidewater. Also at the meeting, the GulfMark Board discussed entering into a new engagement letter for Evercore to act as GulfMark’s financial advisor in connection with a potential transaction with Tidewater and the review of other strategic alternatives.

On February 17, 2018, representatives of Evercore contacted representatives of Lazard to discuss the GulfMark Board’s response to Tidewater’s indication of interest letter. During this call, the Evercore representatives advised the Lazard representatives that GulfMark was willing to engage in further conversations with Tidewater regarding the combination of the two companies and suggested that the two parties begin financial and operational diligence with a focus on developing a view as to synergies before determining an exchange ratio. As instructed by the GulfMark Board, representatives of Evercore noted to representatives of Lazard that the GulfMark Board expected GulfMark stockholders to receive more than a 25% ownership stake in the combined company if a transaction were to proceed.

On February 20, 2017, Lazard delivered to Evercore a draft mutual confidentiality agreement to facilitate the exchange of confidential information between Tidewater and its representatives and GulfMark and its representatives. Thereafter, representatives of Weil and Gibson negotiated the terms of the confidentiality agreement. Tidewater and GulfMark subsequently entered into the confidentiality agreement on March 15, 2018.

On February 22, 2018, the GulfMark Board held a telephonic meeting, together with representatives of Evercore and Gibson, and discussed, among other things, certain considerations of both a standalone plan and a merger with a peer company, including Tidewater and Party X. The directors noted, among other things, the potential for a merger to create a leading company in the industry and the associated benefits to all stockholders. In discussing the standalone alternative, directors and representatives of Evercore discussed that GulfMark was not expected to be cash flow positive until 2020, as well as the risk of potential industry consolidation without GulfMark involved and the negative impact such transactions may have on GulfMark. Also at the meeting, the GulfMark Board approved the terms of Evercore’s new engagement letter for its work as GulfMark’s financial advisor in connection with exploring strategic alternatives. The GulfMark Board determined to continue to work with Evercore due to its familiarity with GulfMark, Tidewater and the OSV sector, as well as its expertise in transactions similar to the potential transaction with Tidewater, and the existence of potential continuing fee obligations pursuant to the previous engagement letter with Evercore.

On March 9, 2018, Mr. Kneen and representatives of Evercore met with representatives of Party X and its financial advisors to discuss a potential business combination transaction. At that meeting, Party X indicated a possible interest in pursuing a strategic acquisition of GulfMark and that any potential transaction between the parties would be structured as an all-stock transaction at the current market values for both companies.

On March 12, 2018, the GulfMark Board held a telephonic meeting and Mr. Kneen reported on the discussions with Party X. During such meeting, the GulfMark Board, along with representatives of Gibson and Evercore, also discussed the status of negotiations with Tidewater regarding the mutual confidentiality agreement.

On March 20, 2018, the Tidewater Board held a meeting. During this meeting, the Tidewater Board discussed various strategic opportunities that could be available to Tidewater and representatives of Lazard reviewed with the Tidewater Board various potential acquisition targets, including GulfMark. Representatives of Lazard also updated the Tidewater Board concerning the status of the discussions with GulfMark. Following this discussion,

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the Tidewater Board determined it appropriate to continue discussions with GulfMark to determine whether or not a potential transaction was more favorable to Tidewater than other opportunities available to Tidewater.

On March 20, 2018, the GulfMark Board held a meeting in New York City, at the offices of Gibson, where the directors and representatives of Evercore and Gibson continued discussion regarding potential transactions with Party X and Tidewater.

On March 21, 2018, senior management of Tidewater and representatives of Lazard met with senior management of GulfMark and representatives of Evercore to discuss the potential strategic transaction between Tidewater and GulfMark and the synergies that could potentially be obtained as a result of such transaction.

Later on March 21, 2018, the GulfMark Board held a telephonic meeting, together with representatives of Evercore and Gibson, to discuss the meeting with Tidewater and discuss next steps, which included continued due diligence and analysis of potential synergies.

On March 23, 2018, representatives of Lazard and Evercore discussed the respective cost structures of Tidewater and GulfMark and identified areas of potential synergies between the two companies.

On March 28, 2018, Mr. Kneen received a letter from Party X indicating that Party X was interested in pursuing a transaction with GulfMark in an all-stock transaction at the current market values for both companies.

On March 29, 2018 and April 4, 2018, senior management of Tidewater and GulfMark, along with representatives of Lazard and Evercore, continued to discuss further areas where synergies could be created in a combination of Tidewater and GulfMark.

On April 12, 2018, Mr. Kneen received a letter from Party X stating that Party X had decided to terminate merger discussions with GulfMark. As described below, GulfMark was later informed by Party X that Party X’s decision to terminate discussions was the result of legal constraints on Party X (unrelated to GulfMark).

On April 13, 2018, the Tidewater Board held a meeting to discuss the status of the discussions with GulfMark. Representatives of senior management, Lazard and Weil attended the meeting. During this meeting, Mr. Bates updated the Tidewater Board on the status of the discussions with GulfMark. Representatives of Lazard presented to the Tidewater Board a preliminary analysis of a potential combination between Tidewater and GulfMark and the parties’ views as to the synergies that could potentially be created as a result of such combination. At the conclusion of the Tidewater Board meeting, the Tidewater Board authorized management to prepare and deliver an updated indication of interest letter to GulfMark proposing a 1.00 exchange ratio for each issued and outstanding share of GulfMark common stock.

On April 16, 2018, Mr. Raspino received a letter from Mr. John T. Rynd, President, Chief Executive Officer and Director of Tidewater, proposing a 1.00 exchange ratio for each issued and outstanding share of GulfMark common stock or creditor warrant. The letter indicated that this proposed exchange ratio would result in GulfMark stockholders receiving a 25% ownership stake in the combined company (24% on a fully-diluted basis).

On April 16, 2018, representatives of Lazard and Evercore discussed certain diligence questions and clarified certain areas of synergies previously identified by the parties, the exchange ratio offered by Tidewater for each issued and outstanding share of GulfMark common stock and the proposed treatment of other equity securities of GulfMark in the potential combination.

On April 16, 2018, the GulfMark Board, together with representatives of Evercore and Gibson, met telephonically and received an update from representatives of Evercore on the continued financial due diligence of Tidewater and the synergy analysis. The GulfMark Board also discussed with its advisors the revised indication of interest letter received from Tidewater, and the March 28, 2018 and April 12, 2018 letters received from Party X.

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On April 18, 2018, the GulfMark Board held a telephonic meeting, together with representatives of Evercore and Gibson, to further discuss the April 16 letter Mr. Raspino received from Mr. Rynd. Following a discussion among directors, the GulfMark Board instructed Evercore to communicate to Lazard that Tidewater would need to increase its offer above the proposed 25% pro forma ownership split.

On April 18, 2018, following the GulfMark Board meeting, representatives of Evercore called representatives of Lazard to explain that the latest Tidewater offer was not satisfactory to the GulfMark Board and that Tidewater would need to increase its offer above the proposed 25% pro forma ownership split.

On April 21, 2018, Mr. McCarty called Mr. Bates and proposed that the parties consider a transaction in which GulfMark stockholders would hold approximately 30% of the pro forma equity of the combined company. Mr. McCarty further requested a meeting among the respective senior management of the companies to discuss the parties’ differing views on valuation.

On April 23, 2018, Mr. Kneen and Mr. Traub met with the Chief Executive Officer of Party X in New York City who explained that he was interested in further discussions regarding a potential transaction, but noted that legal constraints on Party X (unrelated to GulfMark) would prevent such discussions in the near term.

On April 24, 2018, representatives of Lazard and Evercore discussed the respective assumptions and analysis used by Tidewater and GulfMark in their respective valuation assessments of the potential combination.

On April 26, 2018, Messrs. Bates, Rynd and Fanning from Tidewater and Messrs. Kneen and McCarty from GulfMark, together with representatives of Lazard and Evercore, met to discuss the respective parties’ differing views on valuation. At the conclusion of the meeting, Mr. Bates indicated that he and Tidewater management could support a transaction in which GulfMark stockholders would be able to expect to receive 26% of the pro forma equity ownership of the combined company.

On April 27, 2018, the GulfMark Board held a telephonic meeting, together with representatives of Evercore and Gibson, to discuss the recent meeting with Tidewater and Lazard. The directors discussed the proposed 26% pro forma ownership split and potential responses to Tidewater. During such meeting, upon request of the GulfMark Board, representatives of Evercore provided the directors with further background information about Party X. Following such discussion, the GulfMark Board authorized Mr. Traub to contact the Chief Executive Officer of Party X and encourage Party X to submit a new proposal to GulfMark.

Following the April 27 GulfMark Board meeting, Mr. Traub called the Chief Executive Officer of Party X. During the call, Mr. Traub encouraged Party X to submit a new offer to combine with GulfMark. Following such call Mr. Kneen received a call from the Chief Executive Officer of Party X who expressed continuing interest in an at-market transaction.

On April 30, 2018, a representative of Evercore received a call from a representative of Party X’s financial advisor noting the potential upside in a transaction between GulfMark and Party X, but noting that Party X would be unlikely to deliver any control premium in a transaction.

On May 1, 2018, the Tidewater Board held a meeting. During this meeting, Lazard updated the Tidewater Board regarding the status of discussions with GulfMark and provided a preliminary analysis of the potential transaction at various prices. Following this discussion, the Tidewater Board determined it appropriate to continue discussions with GulfMark to determine whether or not a potential transaction was more favorable to Tidewater than other opportunities available to Tidewater.

On May 2, 2018, the GulfMark Board held a telephonic meeting, together with representatives of Evercore and Gibson, to discuss the follow-up discussions with Party X. Representatives of Evercore provided the directors with a more detailed review of the Party X businesses and operations and a summary of the financial due diligence performed to date on Party X. The Evercore representatives also reviewed a summary of the most recent proposals from Party X and Tidewater, including the exchange ratio and resulting implied premiums and discounts at various exchange ratios, and the pro forma equity ownership splits.

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On May 5, 2018, the GulfMark Board held a telephonic meeting, together with representatives of Evercore and Gibson, and discussed giving each of Tidewater and Party X a firm deadline to submit revised “best and final” proposals to encourage one or both of such parties to increase its proposal. Following the meeting, representatives of Evercore contacted Lazard and the financial advisor to Party X requesting that Tidewater and Party X, respectively, submit best and final offers by May 15, 2018.

On May 8, 2018, the GulfMark Board held a telephonic meeting, together with representatives of Evercore and Gibson. The Evercore representatives provided an update on the latest discussions with Tidewater and Party X, and further discussed with the GulfMark Board the strategic rationale to a potential combination with Tidewater or Party X, as well as the considerations of GulfMark as a stand-alone company.

On May 14, 2018, Messrs. Kneen, McCarty and Traub met with representatives of Party X to better understand its business prospects and to encourage a stronger proposal.

Also on May 14, 2018, the Tidewater Board held a meeting to discuss the status of the discussions with GulfMark and GulfMark’s request for a “best and final” proposal. During this meeting, representatives of Lazard updated the Tidewater Board on the status of the discussions with GulfMark, as well as provided updated valuation information to the Tidewater Board. At the conclusion of the meeting, the Tidewater Board authorized management to provide to GulfMark a “best and final” proposal for a stock-for-stock transaction at a 1.10 exchange ratio for each issued and outstanding share of GulfMark common stock.

On May 15, 2018, Mr. Rynd delivered in writing to Mr. Raspino Tidewater’s “best and final” proposal for a stock-for-stock transaction at a 1.10 exchange ratio.

Also on May 15, 2018, Party X’s financial advisor orally conveyed to representatives of Evercore a continued interest in an at market transaction with GulfMark, but did not specify an exchange ratio.

On May 19, 2018, the GulfMark Board held a meeting to discuss the proposals from Tidewater and Party X. Representatives of Evercore and Gibson were in attendance. Among other things, the GulfMark directors provided views on what they believed to be the strong strategic rationales for engaging in a transaction with Tidewater rather than Party X, noting the expected synergies from the transaction with Tidewater and the expectation that the combined company would be a leading OSV operator. The GulfMark directors also discussed with representatives of Evercore the respective valuations of Tidewater versus Party X based on various valuation metrics. The GulfMark directors also discussed the potential governance of the combined company and agreed that it would be appropriate for representatives of Evercore to communicate to Lazard that GulfMark should be entitled to three director seats on the combined company board.

On May 21, 2018, representatives of Evercore informed representatives of Lazard that the GulfMark Board had determined to pursue a transaction with Tidewater. Accordingly, the GulfMark Board was prepared to continue negotiations with Tidewater on the basis of Tidewater’s 1.10 exchange ratio and requested that the Tidewater Board be willing to appoint three GulfMark designated directors on the board of the combined company.

On May 22, 2018, the GulfMark Board met and discussed Evercore’s call with Lazard, as well as the process for moving forward with the proposed transaction with Tidewater.

On May 23, 2018, the Tidewater Board held a telephonic meeting, whereby the Tidewater Board agreed to be willing to consider GulfMark’s request to appoint three GulfMark designated directors to the board of the combined company.

Between May 24, 2018 and the execution of the merger agreement on July 15, 2018, Tidewater and its representatives continued to conduct due diligence on GulfMark. During the same period of time, GulfMark and its representatives continued to conduct due diligence on Tidewater.

On May 24, 2018, Mr. Rynd contacted Mr. Kneen, indicating that Tidewater wished to inspect a number of GulfMark’s vessels prior to announcing a transaction. Messrs. Kneen, Raspino, Traub, and McCarty spoke with

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representatives of Gibson and Evercore to discuss the requested vessel inspections. In light of the concerns raised regarding a potential confidentiality leak in connection with Tidewater’s requested vessel inspections, GulfMark communicated to Tidewater that GulfMark could not agree to Tidewater’s requested pre-signing vessel inspections.

During the week of May 28, 2018, reciprocal due diligence continued and included due diligence calls between representatives of Tidewater and GulfMark and their respective advisors.

On May 30, 2018, Weil sent a draft exclusivity letter to Gibson providing for exclusive discussions regarding a proposed transaction between GulfMark and Tidewater.

On May 31, 2018, Weil provided to Gibson an initial draft of the merger agreement. Among other things, the draft merger agreement contemplated a voting agreement to be entered into by certain stockholders of GulfMark holding in the aggregate 34.99% of GulfMark’s shares of common stock, pursuant to which such stockholders would agree, among other things, to vote in favor of the Tidewater transaction.

On June 4, 2018, representatives of Gibson and Weil discussed the May 31 draft of the merger agreement and Tidewater’s request for exclusivity. Gibson representatives indicated that GulfMark would not proceed with exclusivity until the resolution of various issues raised by the initial draft of the merger agreement, including the size of the proposed termination fee and the proposed treatment of GulfMark’s outstanding debt. Later on June 4, representatives of Weil contacted representatives of Gibson to indicate that Tidewater was prepared to move forward without exclusivity, and Gibson should prepare a full markup of the merger agreement.

On June 11, 2018, Gibson sent a revised draft of the merger agreement to Weil, reflecting the revisions discussed during the call on June 4. In addition, the draft provided that the voting agreement had to terminate in the event the GulfMark Board changed its recommendation with respect to the Tidewater transaction.

Between June 11, 2018 and July 15, 2018, Gibson and Weil continued negotiating the merger agreement in consultation with GulfMark and Tidewater. The main issues that were negotiated were the size of the parties’ termination fees, whether the voting agreement would survive a change of recommendation by the GulfMark Board, the deal protections, the relative scope of the parties’ representations, warranties and covenants (including the operating covenants), and the treatment of GulfMark’s outstanding long-term debt.

On June 13, 2018, a representative of Stephens Inc. (“Stephens”) contacted Mr. Traub on behalf of Harvey Gulf International Marine (“Harvey Gulf”), another OSV owner and operator, requesting a call regarding potential strategic discussions between GulfMark and Harvey Gulf. At that time, Harvey Gulf was in bankruptcy proceedings. Mr. Traub informed representatives of Gibson and Evercore of the request and, following discussion, it was agreed that a representative of Evercore would call Stephens to have an advisor-to-advisor discussion. During such discussion, the Evercore representative confirmed that Stephens had in fact been engaged by Harvey Gulf. Representatives of Stephens then indicated that Harvey Gulf was interested in a potential business combination with GulfMark. Representatives of Evercore noted to Stephens that the GulfMark Board would consider any proposals in accordance with their fiduciary duties and encouraged Stephens to have Shane Guidry, Chief Executive Officer of Harvey Gulf, call Mr. Kneen. Between June 13, 2018 and August 1, 2018, neither Mr. Kneen nor representatives of Evercore received any further communications from Mr. Guidry or Stephens.

On June 21, 2018, Messrs. McCarty, Raspino and Traub had a teleconference with Mr. Bates of Tidewater to express a continued interest in a transaction with Tidewater at the current market values for both companies, which would imply an exchange ratio of 1.16, and to discuss, among other things, open contractual matters.

Later that evening, Mr. Bates updated the Tidewater Board on a teleconference call. The Tidewater Board reiterated that the 1.10 exchange ratio was Tidewater’s “best and final” proposal and that it was unwilling to revise the exchange ratio to reflect the then-current market prices.

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On June 27, 2018, representatives of Evercore advised representatives of Lazard that GulfMark remained interested in completing a transaction with Tidewater and resolving the current open points in the merger agreement.

On June 28, 2018, senior management of Tidewater and GulfMark, together with representatives of Lazard, Evercore, Weil and Gibson, discussed the respective parties’ views as to various open points in the merger agreement.

On July 2, 2018, Messrs. Kneen, Rynd and Fanning met in person at the Houston offices of Evercore to discuss certain provisions of the merger agreement, including the operating covenants. During that meeting, Messrs. Rynd and Fanning reiterated Tidewater’s request to conduct vessel inspections prior to any announcement of a transaction.

On July 4, 2018, representatives of Weil sent a revised draft of the merger agreement to representatives of Gibson. The revised merger agreement contemplated that the voting agreement would not terminate in the event of a change of recommendation by the GulfMark Board and proposed a termination fee payable by GulfMark of $13 million and by Tidewater of $35 million in certain circumstances.

On July 5, 2018, Weil delivered to Gibson an initial draft of the voting agreement pursuant to which certain stockholders of GulfMark would be required, subject to the terms and conditions set forth in such voting agreement, to vote certain of the shares that they owned in favor of the transaction.

On July 8, 2018, Gibson sent a revised draft of the merger agreement to Weil. The revised draft accepted Tidewater’s proposed termination fees, but required the termination of the proposed voting agreement in the event of a change of recommendation by the GulfMark Board. The remaining material outstanding issues included vessel inspections, which Tidewater continued to insist be completed before signing of the merger agreement.

On July 9, 2018, the GulfMark Board held a telephonic meeting with representatives of Gibson and Evercore to discuss the outstanding material issues in the merger agreement. The GulfMark Board then authorized members of the GulfMark Board and representatives of Gibson and Evercore to meet with representatives of Tidewater to negotiate the outstanding material issues in the merger agreement.

On July 9, 2018, the Tidewater Board held a telephonic meeting, with representatives of Weil and Lazard in attendance. During this meeting, representatives of Weil reviewed with the Tidewater Board their fiduciary duties under Delaware law in connection with the consideration of a transaction with GulfMark, and reviewed with the Tidewater Board the terms of the current draft of the merger agreement as well as the remaining open issues with GulfMark.

On July 10, 2018, Messrs. Rynd, Bates, Fanning and Lundstrom, together with representatives of Lazard and Weil, met with Messrs. Raspino, Kneen, McCarty and Traub, together with representatives of Evercore and Gibson in the offices of Lazard in Houston, Texas to discuss the remaining open business issues in the merger agreement, the voting agreement and open diligence requests from Tidewater. Among other things, the parties agreed that the voting agreement would terminate in the event GulfMark’s Board changed its recommendation with respect to the Tidewater merger. GulfMark also agreed to allow Tidewater to conduct limited vessel inspections prior to signing of the merger agreement.

From July 10, 2018 to July 15, 2018, Gibson and Weil exchanged drafts of the merger agreement, disclosure schedules and other ancillary agreements.

On July 12, 2018, counsel to Raging and Captain Q delivered to Weil their comments to the draft voting agreement.

Later that evening, the Tidewater Board held a telephonic meeting. Representatives of Lazard and Weil attended the meeting. Tidewater senior management first updated the Tidewater Board on the status of the negotiations

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with GulfMark. Representatives of Weil also reviewed with the Tidewater Board their fiduciary duties under Delaware law in connection with the consideration of a transaction with GulfMark, and updated the Tidewater Board on the resolution of the open issues in the merger agreement and the voting agreement. Representatives of Lazard also provided the Tidewater Board with its updated financial analyses with respect to the proposed transaction. Tidewater’s management team also reviewed with the Tidewater Board the anticipated timeline of, and the key considerations relating to, the announcement should the transaction ultimately be approved by the Tidewater Board. At the conclusion of the meeting, the Tidewater Board expressed its unanimous support for continuing to pursue the transaction with GulfMark.

From July 13, 2018 until July 15, 2018, representatives of Weil negotiated the final terms of the merger agreement with representatives of Gibson. In addition, Weil negotiated the terms of the voting agreement with counsel to Raging and Captain Q.

Between the close of market on July 13, 2018 and the morning of July 15, 2018, representatives of Tidewater conducted the requested inspections of certain GulfMark vessels as a part of Tidewater’s diligence efforts.

On July 15, 2018, a meeting of the Tidewater Nominating and Corporate Governance Committee was held to evaluate and discuss Mr. Louis Raspino, Mr. Kenneth Traub and Mr. Robert Tamburrino, the nominees to the Tidewater Board proposed by GulfMark in connection with the proposed transaction. After evaluating and discussing the experience, qualifications and attributes of each of the directors proposed by GulfMark (including by reviewing each such proposed director’s responses to the 2018 Tidewater Inc. Proposed Director Questionnaire and other information available to Tidewater), the Tidewater Nominating and Corporate Governance Committee recommended to the Tidewater Board that each such director nominee be accepted by the Tidewater Board to have a seat on the Tidewater Board immediately following consummation of the business combination.

Following the meeting of the Tidewater Nominating and Corporate Governance Committee, the Tidewater Board held a telephonic meeting to consider the approval of the transaction with GulfMark. Representatives of Lazard and Weil attended this meeting. During this meeting, Tidewater senior management updated the Tidewater Board on the results of the due diligence of GulfMark. Representatives of Weil reviewed with the Tidewater Board the final terms of the merger agreement and the voting agreement. Thereafter, representatives of Lazard presented to the Tidewater Board its financial analysis of the proposed transaction and delivered its oral opinion, which was confirmed by delivery of a written opinion dated as of the same date, to the effect that, as of such date and based upon and subject to the assumptions, qualifications, limitations and other matters set forth in such opinion, the aggregate merger consideration to be paid by Tidewater was fair, from a financial point of view, to Tidewater. After considering and discussing the foregoing and the proposed terms of the merger agreement, and taking into consideration the factors described in the sections titled “The Business Combination—Recommendation of the Tidewater Board and Reasons for the Business Combination,” and “The Business Combination—Opinion of Lazard, Tidewater’s Financial Advisor” beginning on page 86 and page 89, respectively, the members of the Tidewater Board unanimously (i) determined that the merger agreement, the voting agreements with each of Raging and Captain Q, the mergers and the other transactions contemplated thereby were fair to and in the best interests of Tidewater and its stockholders, (ii) approved and declared it advisable that Tidewater enter into the merger agreement and the voting agreements with each of Raging and Captain Q and (iii) recommended the approval of the issuance of Tidewater common stock by Tidewater’s stockholders and directed that the issuance of Tidewater common stock in connection with the business combination be submitted to Tidewater’s stockholders for their approval at Tidewater’s special meeting.

On July 15, 2018, the GulfMark Board held a telephonic meeting with members of GulfMark management and representatives of Evercore and Gibson in attendance. During the meeting, representatives of Gibson reviewed the fiduciary duties of the GulfMark Board in connection with reviewing a potential transaction with Tidewater, updated the GulfMark Board regarding the outcome of the points in the transaction documents that had remained

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open at the prior GulfMark Board meeting, and reviewed with the GulfMark Board the resolutions that it would be adopting if it determined to enter into the potential transaction with Tidewater. Representatives of Evercore then reviewed with the GulfMark Board its final financial analysis of the exchange ratio provided for in the merger agreement. Representatives of Evercore then delivered to the GulfMark Board its oral opinion, confirmed by its delivery of a written opinion dated July 15, 2018, that, as of the date thereof, and based upon and subject to the assumptions, procedures, factors, qualifications, limitations and other matters set forth in Evercore’s written opinion, the exchange ratio pursuant to the merger agreement was fair, from a financial point of view, to the holders of GulfMark common stock entitled to receive the merger consideration in the first merger. Following further discussion, the GulfMark Board thereafter unanimously determined that (i) the merger agreement and the consummation of the transactions contemplated thereby, including the mergers, are fair to, and in the best interests of GulfMark and its stockholders, (ii) authorized, approved and declared advisable the merger agreement and the transactions contemplated thereby, including the mergers, and (iii) recommended that GulfMark stockholders vote in favor of the adoption and approval of the merger agreement. The GulfMark Board also unanimously resolved that the merger agreement be submitted for consideration and approval by the GulfMark stockholders entitled to vote at the GulfMark special meeting and recommended that the GulfMark stockholders approve the merger agreement at the GulfMark special meeting.

Later that evening, the voting agreements were executed by Tidewater, Raging and Captain Q. Pursuant to the voting agreements, Raging and Captain Q each agreed, on the terms and subject to the conditions set forth in their respective voting agreement, to vote an aggregate of 2,624,346 of shares of GulfMark common stock (representing approximately 34.99% of the outstanding shares of GulfMark common stock as of July 15, 2018), of which 1,709,464 shares are beneficially owned by Raging and 914,882 shares are beneficially owned by Captain Q, in favor of the approval of the GulfMark merger proposal and the approval of the transactions contemplated by the merger agreement. Thereafter, the merger agreement was executed and delivered by Tidewater and GulfMark.

On the morning of July 16, 2018, prior to the commencement of trading on the New York Stock Exchange, Tidewater and GulfMark issued a joint press release announcing the entering into of the merger agreement.

On August 1, 2018, Mr. Shane Guidry, Chief Executive Officer of Harvey Gulf, contacted Mr. Kneen telephonically to indicate that Harvey Gulf would be submitting a letter to GulfMark proposing a business combination transaction between GulfMark and Harvey Gulf. Later that day, Mr. Kneen received the letter from Mr. Guidry proposing to combine the companies through a merger in which GulfMark would acquire Harvey Gulf, with the combined company remaining publicly listed. Pursuant to the Harvey Gulf proposal, GulfMark stockholders would own 41.2% pro forma equity of the combined company.

On August 5, 2018, the GulfMark Board held a telephonic meeting with representatives of Evercore, Gibson and Richards, Layton and Finger LLP, Delaware counsel to GulfMark (“Richards Layton”), to discuss the August 1, 2018 letter from Harvey Gulf. During such meeting, representatives of Gibson and Richards Layton reviewed with the GulfMark Board its fiduciary duties and GulfMark’s obligations under the merger agreement. In addition, representatives of Evercore reviewed publicly-available financial information regarding Harvey Gulf. During such meeting the GulfMark Board did not make a determination as to whether the Harvey Gulf proposal “could reasonably be expected to result in a “Company Superior Offer” (as defined in the merger agreement). Instead, the GulfMark Board authorized Gibson and Evercore to seek a waiver from Tidewater under the merger agreement in order to allow GulfMark to request further information from Harvey Gulf.

On August 6, 2018, the Tidewater Board held a telephonic meeting to discuss the developments with respect to the Harvey Gulf proposal and GulfMark’s request for a waiver under the merger agreement in order to allow GulfMark to request further information from Harvey Gulf with respect to the Harvey Gulf proposal. Representatives of management, Lazard and Weil attended the meeting. During that meeting, representatives of Lazard reviewed with the Tidewater Board the terms of the Harvey Gulf proposal. Representatives of Weil reviewed with the Tidewater Board the obligations of GulfMark under the merger agreement, Tidewater’s rights

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with respect thereto and the request by GulfMark for a waiver under the merger agreement in order to allow GulfMark to request further information from Harvey Gulf with respect to the Harvey Gulf proposal. At the conclusion of the meeting, the Tidewater Board authorized management to grant the requested waiver.

On August 7, 2018, Tidewater granted the waiver requested by GulfMark, and on such date GulfMark delivered a letter to Harvey Gulf requesting specific due diligence materials. Harvey Gulf delivered some of the requested materials by means of an electronic data room.

On August 12, 2018, the Tidewater Board held a telephonic meeting to further discuss the Harvey Gulf proposal. Representatives of management, Lazard and Weil attended the meeting. During that meeting, representatives of Lazard reviewed with the Tidewater Board Lazard’s analysis of the Harvey Gulf proposal. Representatives of Weil again reviewed with the Tidewater Board the obligations of GulfMark under the merger agreement and Tidewater’s rights with respect thereto. At the conclusion of the meeting, the Tidewater Board requested that management continue to update the Tidewater Board with respect to any further developments in connection with the Harvey Gulf proposal.

On August 14, 2018, the GulfMark Board held a telephonic meeting with representatives of Evercore, Gibson and Richards Layton to further discuss the August 1, 2018 letter from Harvey Gulf. During such meeting, representatives of Gibson and Richards Layton reviewed with the GulfMark Board its fiduciary duties and GulfMark’s obligations under the merger agreement. In addition, representatives of Evercore reviewed publicly-available financial information and information made available in the diligence materials received from Harvey Gulf. During such meeting the GulfMark Board (i) concluded in good faith, after consulting with its outside legal counsel and financial advisors, that the Harvey Gulf proposal could reasonably be expected to result in a Company Superior Offer and (ii) authorized members of the GulfMark Board, management and its advisors to proceed to engage in discussions with Harvey Gulf, subject to the terms of the merger agreement, to further evaluate Harvey Gulf’s proposed transaction. Following the meeting, GulfMark notified Tidewater of the GulfMark Board’s conclusion in accordance with the merger agreement. Later that evening, management at Tidewater updated the Tidewater Board on the actions taken by the GulfMark Board.

On August 20, 2018, GulfMark and Harvey Gulf entered into a mutual confidentiality agreement to facilitate the exchange of confidential information and discussions between Harvey Gulf and its representatives and GulfMark and its representatives. Following such date, GulfMark and its representatives conducted due diligence on Harvey Gulf, and Harvey Gulf and its representatives conducted due diligence of GulfMark.

On August 23, 2018, representatives of GulfMark and Harvey Gulf met in Houston, Texas to discuss the Harvey Gulf business and financial outlook.

On September 4, 2018, the GulfMark Board held a meeting in New York City together with members of GulfMark management and with representatives of Evercore and Gibson Dunn. During such meeting the GulfMark Board discussed, among other things, the Harvey Gulf business and fleet, based on due diligence that had been conducted to date.

On September 6 and 8, 2018, representatives of Harvey Gulf and Stephens met with GulfMark management and representatives of Evercore telephonically to review Harvey Gulf’s preliminary view on synergies that it believed could be achieved in a combination transaction between Harvey Gulf and GulfMark.

On September 14, 2018, the GulfMark Board held a telephonic meeting together with representatives of Gibson Dunn and Evercore. Representatives of Evercore provided an update on the financial due diligence conducted and its preliminary views on valuation of Harvey Gulf.

On September 19, 2018, a representative of Stephens communicated to a representative of Evercore that the Harvey Gulf board of directors had unanimously approved an increase to Harvey Gulf’s previously communicated proposal and such increased proposal would be presented at a meeting between representatives of Harvey Gulf management and members of the GulfMark Board.

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On September 27, 2018, several directors and management of Tidewater met with several directors and management of GulfMark in Houston, Texas to review the synergies that could potentially be achieved following the completion of the business combination.

On October 2, 2018, members of the GulfMark Board, along with representatives of Evercore and Gibson Dunn, met with Mr. Shane Guidry and other members of Harvey Gulf management along with members of the Harvey Gulf board of directors, certain Harvey Gulf stockholders and representatives of the legal and financial advisors to Harvey Gulf in New York City. During such meeting, Harvey Gulf presented GulfMark with a revised proposal pursuant to which GulfMark stockholders would own 42.46%, on a fully-diluted basis. The materials delivered by Harvey Gulf representatives at the meeting represented that Harvey Gulf’s new proposal reflected a revised enterprise value for Harvey Gulf of $850 million, a downward revision of $50 million from the initial August 1, 2018 letter. In addition, Harvey Gulf proposed that the board of directors of the combined company would consist of four independent directors appointed by the existing GulfMark Board, five independent directors from Harvey Gulf’s current board of directors and two members to be nominated by Mr. Shane Guidry. During this meeting, members of the GulfMark Board expressed to the representatives of Harvey Gulf their concerns with respect to the Harvey Gulf proposal, including (1) Harvey Gulf’s expressed valuation reflected in its proposal, (2) Harvey Gulf’s balance sheet and the anticipated pro forma debt of the combined company in a Harvey Gulf/GulfMark combination, (3) the proposed combined company board composition, (4) the proposed combined company management team and (5) the expected trading dynamics of the combined company’s stock.

On October 8, 2018, the GulfMark Board held a telephonic meeting together with representatives of Gibson Dunn and Evercore to discuss the October 2, 2018 meeting with Harvey Gulf, and the revised proposal from Harvey Gulf. Among other things, the members of the GulfMark Board discussed the concerns that had been previously discussed and raised with Harvey Gulf representatives at the October 2, 2018 meeting with Harvey Gulf, including (1) Harvey Gulf’s expressed valuation, (2) Harvey Gulf’s balance sheet and the anticipated pro forma debt of the combined company, (3) the combined company’s board composition, (4) the combined company’s management team and (5) the expected trading dynamics of the combined company’s stock. The GulfMark Board also discussed the possibility of utilizing the potential competitive dynamics created by the Harvey Gulf proposal to improve the terms of the Tidewater business combination. In that regard, the GulfMark Board authorized Mr. Raspino and Mr. Traub to contact Mr. Bates to encourage Tidewater to increase the exchange ratio to be payable to GulfMark stockholders upon completion of the business combination, and secure additional GulfMark designees on the combined company’s board committees and senior management team. The GulfMark Board noted, as it had in the past, that it believed the retention of Mr. Kneen by the combined company management team would be highly valuable given his knowledge and expertise of GulfMark’s business and operations.

On October 9, 2018, during a meeting among a representative of Evercore and a member of GulfMark management and members of Harvey Gulf management in Houston, Texas, Mr. Guidry indicated that Harvey Gulf may make a cash offer for GulfMark.

On October 10, 2018, Mr. Raspino and Mr. Traub contacted Mr. Bates by telephone and discussed the GulfMark Board requests regarding potential revised terms of the business combination. Mr. Bates indicated that he would discuss these matters with the Tidewater Board, but noted that he strongly believed that the Tidewater Board would be unwilling to adjust the exchange ratio, and that any decisions around board committee compositions and potential management roles would likely not be determined until after closing of the proposed business combination.

Later on October 10, 2018, a representative of Stephens delivered to GulfMark written confirmation of the Harvey Gulf proposal discussed at the October 2 meeting in New York City.

On the morning of October 11, 2018, the GulfMark Board held a telephonic meeting, along with representatives of Evercore, Gibson Dunn and RLF. During the meeting, representatives of Evercore reviewed the financial terms of the revised proposal from Harvey Gulf, which included a detailed forecast of Harvey Gulf prepared by GulfMark management, and valuation analyses and sensitivities thereto. In preparing the Harvey Gulf forecast,

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GulfMark management was assisted by an outside consulting firm with respect to certain assumptions relating to the multi-purpose support vessel (“MPSV”) market. Representatives of the outside consulting firm participated in the portion of the GulfMark Board meeting in which the Harvey Gulf forecast was discussed and were then excused from the meeting. During the meeting the GulfMark Board noted: (1) GulfMark’s management optimized operational efficiencies and estimated synergies of approximately $10 million to $15 million annually in a transaction with Harvey Gulf; (2) Harvey Gulf’s cash flow generation and contract backlog; (3) the attributes of Harvey Gulf’s fleet, including its extra-large OSVs and MPSVs with a deepwater focus; and (4) Harvey Gulf’s customer relationships. However, the GulfMark Board also considered: (1) the lack of a public market valuation available for Harvey Gulf; (2) the lack of public market experience of Harvey Gulf’s management team; (3) the apparent strong dependence of Harvey Gulf on Mr. Guidry; (4) Harvey Gulf’s less diversified fleet with concentrated market exposure to the Gulf of Mexico; (5) that the proposed combined company board would likely be dominated by current Harvey Gulf directors and Mr. Guidry (who would individually have the right to appoint two directors under the October 2 Harvey Gulf proposal); (6) Harvey Gulf’s customer concentration risk; (7) the significant pro forma leverage of the combined company; (8) the likely lower pro forma trading liquidity for GulfMark stockholders in a transaction with Harvey Gulf (as compared to Tidewater); and (9) the delays, risks and uncertainties regarding any potential transaction with Harvey Gulf. At the conclusion of such meeting, the GulfMark Board, after consulting with its financial advisor and outside legal counsel determined that, taking into account the factors described in this paragraph, among others, the proposal from Harvey Gulf is not more favorable from a financial point of view to GulfMark stockholders than the Contemplated Transactions. The GulfMark Board then instructed Evercore to contact Stephens and inquire whether Harvey Gulf will be submitting a cash offer. Such message was conveyed later in the day on October 11, 2018 to Stephens, who noted that a cash proposal was not imminent.

Later on October 11, 2018, Mr. Bates had separate telephonic calls with each of Mr. Raspino and Mr. Traub. During these calls, Mr. Bates confirmed that the Tidewater Board was unwilling to adjust the exchange ratio.

Tidewater also communicated that no final determination regarding the GulfMark Board’s further governance and management requests would be made by the Tidewater Board until after closing of the proposed business combination.

Recommendation of the Tidewater Board and Reasons for the Business Combination

The Tidewater Board unanimously recommends that the Tidewater stockholders vote “FOR” the Tidewater issuance proposal.

The Tidewater Board, with the advice and assistance of its financial and legal advisors, negotiated, evaluated and, at a meeting held on July 15, 2018, unanimously approved the merger agreement, the mergers and the other transactions contemplated by the merger agreement.

In reaching its decision to approve the merger agreement, the mergers and the other transactions contemplated by the merger agreement and to recommend that Tidewater stockholders vote in favor of the Tidewater issuance proposal, the Tidewater Board consulted with its financial and legal advisors and Tidewater’s management. After such consultation, the Tidewater Board unanimously determined the transactions contemplated by the merger agreement to be in the best interests of Tidewater.

The Tidewater Board’s decision to approve the merger agreement, the mergers and the other transactions contemplated thereby and to recommend that Tidewater stockholders vote in favor of the Tidewater issuance proposal was based on a number of factors, including the following (which are not necessarily presented in order of relative importance):

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In the course of its deliberations, the Tidewater Board also considered a variety of risks, uncertainties and other potentially negative factors, including the following (which are not necessarily presented in order of relative importance):

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The Tidewater Board considered all of these factors as a whole and unanimously concluded that they supported a determination to approve the merger agreement, the business combination and the other transactions contemplated thereby. The foregoing discussion of the information and factors considered by the Tidewater Board is not exhaustive. In view of the wide variety of factors considered by the Tidewater Board in connection with its evaluation of the business combination and the complexity of these matters, the Tidewater Board did not consider it practical to, nor did it attempt to, quantify, rank or otherwise assign relative weights to the specific factors that it considered in reaching its decision. In considering the factors described above and any other factors, individual members of the Tidewater Board may have viewed factors differently or given different weight or merit to different factors.

The foregoing discussion of the information and factors considered by the Tidewater Board is forward-looking in nature. This information should be read in light of the factors described in the section entitled “Cautionary Statement Regarding Forward-Looking Statements” beginning on page 56.

Opinion of Lazard, Tidewater’s Financial Advisor

Tidewater has retained Lazard to act as its financial advisor in connection with the business combination. As part of this engagement, Tidewater requested that Lazard evaluate the fairness, from a financial point of view, to Tidewater of the exchange ratio provided for in the business combination. At a meeting of the Tidewater Board held to approve the business combination on July 15, 2018, Lazard rendered an oral opinion to the Tidewater Board, subsequently confirmed in writing, to the effect that, as of such date, and based upon and subject to the assumptions, procedures, factors, qualifications and limitations set forth in Lazard’s written opinion, the exchange ratio provided for in the business combination was fair, from a financial point of view, to Tidewater.

The full text of Lazard’s written opinion, dated July 15, 2018, which sets forth the assumptions made, procedures followed, factors considered and qualifications and limitations on the review undertaken by Lazard in connection with its opinion, is attached as Annex C to this joint proxy statement/prospectus and is incorporated herein by reference. Tidewater encourages you to read Lazard’s opinion carefully and in its entirety.

Lazard’s opinion was provided for the use and benefit of the Tidewater Board (in its capacity as such) in its evaluation of the business combination, and addressed only the fairness, as of the date of the opinion, from a financial point of view, to Tidewater of the exchange ratio provided for in the business combination. Lazard’s opinion is not intended to and does not constitute a recommendation to any Tidewater stockholder as to how such stockholder should vote or act with respect to the Tidewater issuance proposal.

Lazard’s opinion was necessarily based on economic, monetary, market and other conditions as in effect on, and the information made available to Lazard as of, the date of Lazard’s opinion. Lazard assumed no responsibility for updating or revising its opinion based on circumstances or events occurring after the date of Lazard’s opinion. Lazard’s opinion did not express any opinion as to the price at which Tidewater common stock or GulfMark common stock may trade at any time subsequent to the announcement of the business combination. Lazard’s opinion does not address the relative merits of the business combination as compared to any other business combination or business strategy in which Tidewater might engage or the merits of the underlying decision by Tidewater to engage in the business combination.

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