<PAGE>

                                                                     Exhibit 4.3

THE SECURITIES REPRESENTED BY THIS CERTIFICATE (OR ITS PREDECESSOR) WERE
ORIGINALLY ISSUED IN A TRANSACTION EXEMPT FROM REGISTRATION UNDER THE SECURITIES
ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"), AND SAID SECURITIES MAY NOT BE
OFFERED, SOLD OR OTHERWISE TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR AN
APPLICABLE EXEMPTION THEREFROM. EACH PURCHASER OF SAID SECURITIES IS HEREBY
NOTIFIED THAT THE SELLER OF SAID SECURITIES MAY BE RELYING ON THE EXEMPTION FROM
THE PROVISIONS OF SECTION 5 OF THE SECURITIES ACT PROVIDED BY RULE l44A
THEREUNDER.

THE HOLDER OF SAID SECURITIES AGREES FOR THE BENEFIT OF THE ISSUER THAT (A) SAID
SECURITIES MAY BE OFFERED, RESOLD, PLEDGED OR OTHERWISE TRANSFERRED, ONLY (I) TO
THE ISSUER THEREOF, (II) IN THE UNITED STATES TO A PERSON WHOM THE SELLER
REASONABLY BELIEVES IS A QUALIFIED INSTITUTIONAL BUYER (AS DEFINED IN RULE 144A
UNDER THE SECURITIES ACT) IN A TRANSACTION MEETING THE REQUIREMENTS OF RULE
144A, (III) PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT
PROVIDED BY RULE 144 THEREUNDER (IF AVAILABLE), (IV) TO AN ACCREDITED INVESTOR
IN A TRANSACTION EXEMPT FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT
OR (V) PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT,
IN EACH OF CASES (I) THROUGH (V) IN ACCORDANCE WITH ANY APPLICABLE SECURITIES
LAWS OF THE STATES AND OTHER JURISDICTIONS OF THE UNITED STATES, AND (B) THE
HOLDER WILL, AND EACH SUBSEQUENT HOLDER IS REQUIRED TO, NOTIFY ANY PURCHASER OF
SAID SECURITIES FROM IT OF THE RESALE RESTRICTIONS REFERRED TO IN (A) ABOVE.

THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO THE TERMS OF A
PURCHASE AGREEMENT, DATED AS OF MARCH 11, 2004, AMONG HORIZON OFFSHORE, INC.
(THE "COMPANY"), THE GUARANTORS LISTED ON THE SIGNATURE PAGES THEREOF AND THE
PURCHASERS LISTED ON THE SIGNATURE PAGES THEREOF, AND A REGISTRATION RIGHTS
AGREEMENT, DATED AS OF MARCH 11, 2004, AMONG THE COMPANY AND THE PURCHASERS
LISTED ON THE SIGNATURE PAGES THEREOF, COPIES OF EACH OF WHICH ARE ON FILE AT
THE MAIN OFFICE OF THE COMPANY. ANY SALE OR TRANSFER OF THE SECURITIES EVIDENCED
BY THIS CERTIFICATE IS SUBJECT TO THE TERMS OF THOSE AGREEMENTS AND ANY SALE OR
TRANSFER OF SUCH SECURITIES IN VIOLATION OF SAID AGREEMENTS SHALL BE INVALID.
<PAGE>
Certificate No._____________         WARRANT                      March 11, 2004

                  To Purchase ______ Shares of Common Stock of
                     Horizon Offshore, Inc. (the "Company")

          1. Number of Shares; Remaining Exercise Price; Term. This certifies
that _________ ("Holder") is entitled, upon the terms and other conditions set
forth herein, to acquire from the Company, in whole or in part, from time to
time up to ______ fully paid and nonassessable shares (the "Shares") of common
stock, $1.00 par value per share, of the Company ("Common Stock") at a purchase
price per Share (the "Remaining Exercise Price") equal to $.01, subject to
adjustment as set forth below. The Holder (or its predecessor) is deemed to have
previously paid $0.99 per Share of the exercise price for the Shares upon
initial issuance of this Warrant (or its predecessor). The right to purchase the
shares of Common Stock under this Warrant is exercisable immediately and shall
remain exercisable until March 11, 2009 (the "Exercise Period").

          2. Purchase Price Allocation. For U.S. federal income tax purposes,
(i) the Issuer agrees that the portion of the Purchase Price allocable to the
Notes purchased by Initial Purchasers of Notes and Warrants is $609.04379 per
$1,000 principal amount thereof and that the portion of the Purchase Price
allocable to the Warrants is $3.27526 per Warrant and (ii) each Initial
Purchaser of Notes and Warrants, by accepting this Note, agrees to allocate its
purchase price for the Notes and Warrants in accordance with clause (i).

          3. Exercise of Warrant. The purchase rights represented by this
Warrant are exercisable by the Holder, in whole or in part, at any time during
the Exercise Period by the surrender of this Warrant and the Notice of Exercise
annexed hereto, all duly completed and executed on behalf of the Holder, at the
office of the Company as set forth below the Company's signature hereon (or such
other office or agency of the Company as it may designate by notice in writing
to the Holder at the address of the Holder appearing on the books of the
Company). Payment of the Remaining Exercise Price for the shares of Common Stock
thereby purchased shall be made by cash, certified or cashier's check or wire
transfer payable to the order of the Company, at 10:00 a.m., Central Time, upon
surrender of this Warrant and the Notice of Exercise. Thereupon, the Holder
shall be entitled to receive from the Company a stock certificate in proper form
representing the number of shares of Common Stock so purchased, and a new
Warrant in substantially identical form and dated as of such exercise for the
purchase of that number of Shares equal to the difference, if any, between the
number of shares of Common Stock subject hereto and the number of Shares of
Common stock as to which this Warrant is so exercised.

          4. Issuance of Shares. Certificates for Shares purchased hereunder
shall be delivered to the Holder promptly after the date on which this Warrant
shall have been exercised in accordance with the terms hereof. The Company
hereby represents and warrants that all Shares that may be issued upon the
exercise of this Warrant will, upon such exercise, be duly and validly
authorized and issued, fully paid and nonassessable and free from all taxes,
liens and charges in respect of the issuance thereof (other than liens or
charges created by or imposed upon the Holder as the holder of the Warrant or
taxes in respect of any transfer occurring contemporaneously or otherwise
specified herein). The Company agrees that the Shares so


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<PAGE>
issued shall be and shall for all purposes be deemed to have been issued to the
Holder as the record owner of such Shares as of the close of business on the
date on which this Warrant shall have been exercised or converted in accordance
with the terms hereof.

          5. No Fractional Shares or Scrip. No fractional Shares or scrip
representing fractional Shares shall be issued upon the exercise of this
Warrant. In lieu of any fractional Share to which the Holder would otherwise be
entitled, the Holder shall be entitled to receive a cash payment equal to the
excess of fair market value for such fractional Share above the Remaining
Exercise Price for such fractional share (as determined in good faith by the
Company).

          6. Purchase Agreement. The Warrants evidenced by this Warrant
Certificate are part of a duly authorized issue of Warrants, and are issued or
to be issued pursuant to a Purchase Agreement dated as of March 11, 2004 (the
"Purchase Agreement"), among the Company, the guarantors listed on the signature
pages thereof and the purchasers listed on the signature pagers thereof, which
Purchase Agreement is hereby incorporated by reference in and made a part of
this instrument and is hereby referred to for a description of the rights,
obligations and duties hereunder of the Company and the Holders of the Warrants.
A copy of the Purchase Agreement may be obtained by the holder hereof upon
written request to the Company. Capitalized terms used herein and not defined
herein shall have the meanings assigned to them in the Purchase Agreement.

          7. Registration Rights. The holders of the Warrants are entitled to
certain registration rights as set forth in a Registration Rights Agreement
dated as of March 11, 2004, among the Company and the purchasers listed on the
signature pages thereof (the "Registration Rights Agreement"). A copy of the
Registration Rights Agreement may be obtained by the holder hereof upon written
request to the Company.

          8. No Rights as Stockholders. This Warrant does not entitle the Holder
as a holder hereof to any voting rights or other rights as a stockholder of the
Company prior to the exercise hereof.

          9. Charges; Taxes and Expenses. Certificates for Shares issued upon
exercise of this Warrant shall be issued in the name of the Holder. Issuance of
certificates for Shares upon the exercise of this Warrant shall be made without
charge to the Holder for any issue or transfer tax or other incidental expense
in respect of the issuance of such certificates, all of which taxes and expenses
shall be paid by the Company.

          10. Transfer and Exchange of Warrant. The Company shall from time to
time register the transfer of this Warrant, in whole or in part, in the registry
maintained therefor in accordance with the terms of the Purchase Agreement. In
the event that this Warrant is transferred in part, a new Warrant evidencing the
portion of this Warrant that is not transferred shall be issued and delivered to
the Holder hereof pursuant to the provisions of the Purchase Agreement. The
registered holder of a Warrant will be treated as its owner for all purposes.

     If any transfer of all or a portion of this Warrant is not made pursuant to
an effective registration statement under the Securities Act of 1933, as amended
(the "Securities Act"), (i) the Holder will, if reasonably requested by the
Company, deliver to the Company an opinion of


                                      -3-
<PAGE>
counsel, which may be counsel to the Holder but which must be reasonably
satisfactory to the Company, reasonably satisfactory in form, scope and
substance to the Company, that this Warrant (or portion thereof) may be sold
without registration under the Securities Act; (ii) the proposed transferee
shall make an investment covenant reasonably satisfactory to the Company (except
that no such covenant will be required in connection with a transfer effected in
accordance with Rule 144A under the Securities Act); and (iii) the proposed
transferee shall agree that the Warrant issued to such transferee shall bear the
legend set forth in Section 1.3(e) of the Purchase Agreement.

     Notwithstanding the foregoing provisions of this Section 10, the
restrictions upon the transferability of this Warrant and the requirement to
include the first two paragraphs of the legend set forth in Section 1.3(e) of
the Purchase Agreement shall terminate as to this Warrant (i) when and so long
as this Warrant shall have been effectively registered under the Securities Act
and disposed of pursuant thereto or (ii) when the Company shall have received an
opinion of counsel reasonably satisfactory to it that such restrictive legend is
not required in order to ensure compliance with the Securities Act. Whenever the
restrictions imposed by this Section 10 shall terminate as to this Warrant, the
Holder thereof shall be entitled to receive from the Company a new Warrant
bearing a legend consisting only of the third paragraph of the legend set forth
in Section 1.3(e) of the Purchase Agreement.

     This Warrant is exchangeable, upon the surrender hereof by the Holder as
the registered holder at the above-mentioned office or agency of the Company,
for a new Warrant in substantially identical form and dated as of such exchange,
in accordance with the terms of the Purchase Agreement.

          11. Loss; Theft; Destruction or Mutilation of Warrant. The Company
will replace Warrants upon loss, theft, destruction or mutilation in accordance
with the terms of the Purchase Agreement.

          12. Reservation of Common Stock; Rights. The Company will at all times
that this Warrant is exercisable reserve and keep available, free from
preemptive or similar rights, solely for issuance, sale and delivery upon the
exercise of this Warrant, the maximum number of Warrant Shares which may then be
deliverable upon the exercise of this Warrant. All such Shares shall be duly
authorized and, when issued upon exercise of this Warrant in accordance with the
terms hereof, will be validly issued and fully paid and nonassessable, with no
liability on the part of the Holder. Each Share shall be accompanied by any
rights ("Rights") to which shares of Common Stock are then entitled, pursuant to
the Rights Agreement dated as of January 11, 2002 between the Company and Mellon
Investor Services, LLC, as Rights Agent, as amended, supplemented, modified or
replaced from time to time (the "Rights Agreement"). The Company will at all
times keep authorized, solely for issuance, sale and delivery upon the exercise
of this Warrant, such number of Rights equal to the number of Rights issuable
upon exercise of this Warrant. All such Rights shall be duly authorized and,
when issued upon exercise of this Warrant in accordance with the terms hereof,
will be validly issued.

          13. Listing on Securities Exchanges, etc. The Company will maintain
the listing of all Shares issuable or issued from time to time upon exercise of
this Warrant on each securities exchange or market or trading system on which
any shares of Common Stock are then


                                      -4-
<PAGE>
or at any time thereafter listed or traded, but only to the extent and for such
period of time as such shares of Common Stock are so listed.

          14. Saturdays, Sundays, Holidays, etc. If the last or appointed day
for the taking of any action or the expiration of any right required or granted
herein shall be a Saturday or a Sunday or shall be a legal holiday in New York,
New York, or Houston, Texas, then such action may be taken or such right may be
exercised on the next succeeding day not a Saturday or a Sunday or a legal
holiday in New York, New York, or Houston, Texas.

          15. Adjustments and Termination of Rights. The Remaining Exercise
Price and the number of Shares purchasable hereunder are subject to adjustment
from time to time as follows:

          (a)  Merger or Consolidation. If at any time there shall be a merger
               or a consolidation of the Company with or into another
               corporation when the Company is not the surviving corporation,
               then, as part of such merger or consolidation, lawful provision
               shall be made so that the Holder as the holder of this Warrant
               shall thereafter be entitled to receive upon exercise of this
               Warrant, during the period specified herein and upon payment of
               the aggregate Remaining Exercise Price then in effect, the number
               of shares of stock or other securities or property (including
               cash) of the successor corporation resulting from such merger or
               consolidation, to which the Holder as the holder of the stock
               deliverable upon exercise of this Warrant would have been
               entitled in such merger or consolidation if this Warrant had been
               exercised immediately before such merger or consolidation. In any
               such case, appropriate adjustment shall be made in the
               application of the provisions of this Warrant with respect to the
               rights and interests of the Holder as the holder of this Warrant
               after the merger or consolidation. This provision shall apply to
               successive mergers or consolidations.

          (b)  Reclassification, Recapitalization, etc. If the Company at any
               time shall, by subdivision, combination or reclassification of
               securities, recapitalization, automatic conversion, or other
               similar event affecting the number or character of outstanding
               shares of Common Stock, or otherwise, change any of the
               securities as to which purchase rights under this Warrant exist
               into the same or a different number of securities of any other
               class or classes, this Warrant shall thereafter represent the
               right to acquire such number and kind of securities as would have
               been issuable as the result of such change with respect to the
               securities that were subject to the purchase rights under this
               Warrant immediately prior to such subdivision, combination,
               reclassification or other change.

          (c)  Split, Subdivision or Combination of Shares. If the Company at
               any time while this Warrant remains outstanding and unexpired
               shall split, subdivide or combine the securities as to which
               purchase rights under this Warrant exist, the Remaining Exercise
               Price shall be proportionately


                                      -5-
<PAGE>
               decreased in the case of a split or subdivision or
               proportionately increased in the case of a combination.

          (d)  Common Stock Dividends. If the Company at any time while this
               Warrant is outstanding and unexpired shall pay a dividend with
               respect to Common Stock payable in shares of Common Stock, or
               make any other distribution with respect to shares of Common
               Stock, then the Remaining Exercise Price shall be adjusted, from
               and after the date of determination of the shareholders entitled
               to receive such dividend or distribution, to that price
               determined by multiplying the Remaining Exercise Price in effect
               immediately prior to such date of determination by a fraction (i)
               the numerator of which shall be the total number of shares of
               Common Stock outstanding immediately prior to such dividend or
               distribution, and (ii) the denominator of which shall be the
               total number of shares of Common Stock outstanding immediately
               after such dividend or distribution. This paragraph shall apply
               only if and to the extent that, at the time of such event, this
               Warrant is then exercisable for Common Stock.

          (e)  Adjustment of Number of Shares. Upon each adjustment in the
               Remaining Exercise Price pursuant to Section 15(c) or Section
               15(d) hereof, the number of shares of Common Stock purchasable
               hereunder shall be adjusted, to the nearest whole share, to the
               product obtained by multiplying the number of shares of Common
               Stock purchasable immediately prior to such adjustment in the
               Remaining Exercise Price by a fraction (i) the numerator of which
               shall be the Remaining Exercise Price immediately prior to such
               adjustment, and (ii) the denominator of which shall be the
               Remaining Exercise Price immediately after such adjustment.

          16. Notice of Adjustments; Notices. Whenever the Remaining Exercise
Price or number or type of securities issuable hereunder shall be adjusted
pursuant to Section 15 hereof, the Company shall issue and provide to the Holder
a certificate signed by an officer of the Company setting forth, in reasonable
detail, the event requiring the adjustment, the amount of the adjustment, the
method by which such adjustment was calculated and the Remaining Exercise Price
and number of shares of Common Stock purchasable hereunder after giving effect
to such adjustment.

          17. Governing Law. This Warrant shall be binding upon any successors
or assigns of the Company. This Warrant shall constitute a contract under the
laws of New York and for all purposes shall be construed in accordance with and
governed by the laws of said state without giving effect to the conflict of laws
principles thereof.

          18. Attorneys' Fees. In any litigation, arbitration or court
proceeding between the Company and the Holder as the holder of this Warrant
relating hereto, the prevailing party shall be entitled to reasonable attorneys'
fees and expenses incurred in enforcing this Warrant.


                                      -6-
<PAGE>
          19. Amendments. This Warrant may be amended and the observance of any
term of this Warrant may be waived only with the written consent of the Company
and the Holder.

          20. Notices. All notices hereunder shall be in writing and shall be
effective: at the time delivered by hand, if personally delivered; when
received, if deposited in the mail postage prepaid; when transmission is
verified, if telecopied; and on the next Business Day, if timely delivered to an
air courier guaranteeing overnight delivery, and addressed to the party to be
notified at the address indicated in Section 11.2 of the Purchase Agreement.

          21. Entire Agreement. This Warrant, the forms attached hereto and any
agreements specifically incorporated herein by reference contain the entire
agreement between the parties with respect to the subject matter hereof and
supersede all prior and contemporaneous arrangements or undertakings with
respect thereto.


                                      -7-
<PAGE>
     IN WITNESS WHEREOF, Horizon Offshore, Inc. has caused this Warrant to be
executed by its duly authorized officer.

Dated: March 11, 2004

                                             HORIZON OFFSHORE, INC.

                                             By:
                                                --------------------------------
                                                Name:
                                                Title:

                                             Address:
                                             2500 CityWest Boulevard
                                             Suite 2200
                                             Houston, Texas 77042


                                      -8-
<PAGE>
                               NOTICE OF EXERCISE

To: Horizon Offshore, Inc.

     1.   The undersigned hereby elects to purchase ____________ shares (the
          "Shares") of common stock, $1.00 par value per share, of Horizon
          Offshore, Inc. (the "Company") pursuant to the terms of the attached
          Warrant, and tenders herewith payment of the purchase price and any
          transfer taxes payable pursuant to the terms of the Warrant, together
          with an investment representation statement in form and substance
          satisfactory to legal counsel to the Company.

     2.   The Shares to be received by the undersigned upon exercise of the
          Warrant are being acquired for the undersigned's own account, not as a
          nominee or agent, and not with a view to resale or distribution of any
          part thereof, and the undersigned has no present intention of selling,
          granting any participation in, or otherwise distributing the same,
          except in compliance with applicable federal and state securities
          laws. The undersigned further represents that it does not have any
          contract, undertaking, agreement or arrangement with any person to
          sell, transfer or grant participation to such person or to any third
          person, with respect to the Shares. The undersigned believes the
          undersigned has received all the information it considers necessary or
          appropriate for deciding whether to purchase the Shares.

     3.   The undersigned understands that the Shares are characterized as
          "restricted securities" under the federal securities laws inasmuch as
          they are being acquired from the Company in transactions not involving
          a public offering and that under such laws and applicable regulations
          such securities may be resold without registration under the
          Securities Act of 1933, as amended (the "Act"), only in certain
          limited circumstances. In this connection, the undersigned represents
          that it is familiar with Rule 144 of the Act, as presently in effect,
          and understands the resale limitations imposed thereby and by the Act.

     4.   The undersigned understands the certificates evidencing the Shares may
          bear the following legend:

          (a)  THE SECURITIES REPRESENTED BY THIS CERTIFICATE (OR ITS
               PREDECESSOR) WERE ORIGINALLY ISSUED IN A TRANSACTION EXEMPT FROM
               REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE
               "SECURITIES ACT"), AND SAID SECURITIES MAY NOT BE OFFERED, SOLD
               OR OTHERWISE TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR
               AN APPLICABLE EXEMPTION THEREFROM. EACH PURCHASER OF SAID
               SECURITIES IS HEREBY NOTIFIED THAT THE SELLER OF SAID SECURITIES
               MAY BE RELYING ON THE EXEMPTION FROM THE PROVISIONS OF SECTION 5
               OF THE SECURITIES ACT PROVIDED BY RULE l44A THEREUNDER.
<PAGE>
               THE HOLDER OF SAID SECURITIES AGREES FOR THE BENEFIT OF THE
               ISSUER THAT (A) SAID SECURITIES MAY BE OFFERED, RESOLD, PLEDGED
               OR OTHERWISE TRANSFERRED, ONLY (I) TO THE ISSUER THEREOF, (II) IN
               THE UNITED STATES TO A PERSON WHOM THE SELLER REASONABLY BELIEVES
               IS A QUALIFIED INSTITUTIONAL BUYER (AS DEFINED IN RULE 144A UNDER
               THE SECURITIES ACT) IN A TRANSACTION MEETING THE REQUIREMENTS OF
               RULE 144A, (III) PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER
               THE SECURITIES ACT PROVIDED BY RULE 144 THEREUNDER (IF
               AVAILABLE), (IV) TO AN ACCREDITED INVESTOR IN A TRANSACTION
               EXEMPT FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT
               OR (V) PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE
               SECURITIES ACT, IN EACH OF CASES (I) THROUGH (V) IN ACCORDANCE
               WITH ANY APPLICABLE SECURITIES LAWS OF THE STATES AND OTHER
               JURISDICTIONS OF THE UNITED STATES, AND (B) THE HOLDER WILL, AND
               EACH SUBSEQUENT HOLDER IS REQUIRED TO, NOTIFY ANY PURCHASER OF
               SAID SECURITIES FROM IT OF THE RESALE RESTRICTIONS REFERRED TO IN
               (A) ABOVE.

               THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO THE
               TERMS OF A PURCHASE AGREEMENT, DATED AS OF MARCH 11, 2004, AMONG
               HORIZON OFFSHORE, INC. (THE "COMPANY"), THE GUARANTORS LISTED ON
               THE SIGNATURE PAGES THEREOF AND THE PURCHASERS LISTED ON THE
               SIGNATURE PAGES THEREOF, AND A REGISTRATION RIGHTS AGREEMENT,
               DATED AS OF MARCH 11, 2004, AMONG THE COMPANY AND THE PURCHASERS
               LISTED ON THE SIGNATURE PAGES THEREOF, COPIES OF EACH OF WHICH
               ARE ON FILE AT THE MAIN OFFICE OF THE COMPANY. ANY SALE OR
               TRANSFER OF THE SECURITIES EVIDENCED BY THIS CERTIFICATE IS
               SUBJECT TO THE TERMS OF THOSE AGREEMENTS AND ANY SALE OR TRANSFER
               OF SUCH SECURITIES IN VIOLATION OF SAID AGREEMENTS SHALL BE
               INVALID.

          (b)  Any legend required by applicable state law.

     5.   Please issue a certificate or certificates representing said Shares in
          the name of the undersigned.

                                             -----------------------------------
                                                     [Name of Holder]


                                      -2-
<PAGE>
     6.   Please issue a new Warrant for the unexercised portion of the attached
          Warrant in the name of the undersigned.

                                             -----------------------------------
                                                     [Name of Holder]

                                             -----------------------------------
                                                     [Signature]


                                      -3-