Document:

<PAGE>
                                                                     EXHIBIT 4.3

                               SECOND AMENDMENT TO
             SECOND AMENDED AND RESTATED LOAN AND SECURITY AGREEMENT

         THIS SECOND AMENDMENT TO SECOND AMENDED AND RESTATED LOAN AND SECURITY
AGREEMENT (this "Second Amendment") is made and entered into this 30th day of
August, 2002, by and among FLEET CAPITAL CORPORATION, a Rhode Island corporation
(in its individual capacity, "Fleet"), successor in interest by assignment to
Shawmut Capital Corporation ("Shawmut"), SOUTHWEST BANK OF TEXAS, N.A., a
national banking association ("Southwest"); WHITNEY NATIONAL BANK, a national
banking association ("Whitney"); (Fleet, Whitney and Southwest being referred to
herein collectively as the "Lenders"), Fleet as Agent for the Lenders (the
"Agent"); CANYON OFFSHORE, INC. ("Canyon"), a Texas corporation; CAL DIVE
INTERNATIONAL, INC., a Minnesota corporation ("Cal Dive") and ENERGY RESOURCE
TECHNOLOGY, INC., a Delaware corporation ("ERT") (Cal Dive, ERT, and Canyon
being referred to individually and collectively as the "Borrower").

                                    RECITALS

         A.       The Borrower, Aquatica, Inc., the Agent and the Lenders
                  entered into that certain Second Amended and Restated Loan and
                  Security Agreement (as amended, modified and supplemented from
                  time to time, the "Loan Agreement"), dated as of February 22,
                  2002.

         B.       The Borrower, Aquatica, Inc., the Agent and the Lenders
                  entered into that certain First Amendment to Second Amended
                  and Restated Loan and Security Agreement dated August 9, 2002.

         C.       Aquatica, Inc., a Borrower under the Loan Agreement merged
                  with Cal Dive, with Cal Dive as the surviving entity, pursuant
                  to the Articles of Merger dated June 27, 2002.

                                    ARTICLE I
                                   DEFINITIONS

         1.01 The Borrower, the Agent and the Lenders have agreed to amend the
Loan Agreement to, among other things, temporarily increase the Revolving Credit
Commitment, to waive breaches of certain covenants and to modify certain
covenants, based upon the terms and conditions set forth in this Second
Amendment.

         NOW THEREFORE, in consideration of the premises herein contained and
other good and valuable consideration, the receipt and sufficiency of which are
hereby acknowledged, the parties, intending to be legally bound, agree as
follows:

                                       1
<PAGE>

                                   ARTICLE II
                                   DEFINITIONS

         2.01 Capitalized terms used in this Second Amendment are defined in the
Loan Agreement, as amended hereby, unless otherwise stated.

                                   ARTICLE III
                                   AMENDMENTS

         3.01 TEMPORARY INCREASE IN REVOLVING CREDIT COMMITMENT.

                  (a)      From the date of this Second Amendment up to and
                           including October 29, 2002 the Revolving Credit
                           Commitment as at any date of determination shall be
                           increased to an amount equal to (a) Sixty Seven
                           Million Dollars ($67,000,000) minus ((b) the face
                           amount of all Credit Enhancements outstanding on such
                           date.

                  (b)      Each Lender's portion of the temporary Seven Million
                           Dollars ($7,000,000) increase in the Revolving Credit
                           Commitment is set forth on Schedule 1 to this Second
                           Amendment.

                  (c)      After October 29, 2002, the Revolving Credit
                           Commitment shall automatically and without any
                           further action by the Agent or the Lenders revert to
                           an amount equal to (a) Sixty Million Dollars
                           ($60,000,000) minus (b) the face amount of all Credit
                           Enhancements outstanding on the date of
                           determination.

                  (d)      In consideration for the temporary increase in the
                           Revolving Credit Commitment provided for in this
                           Section 2.01, the Borrower shall pay to the Agent on
                           the date of this Second Amendment, for distribution
                           to those Lenders participating in such temporary
                           increase, a commitment increase fee of $50,000.00.

         3.02 BORROWING BASE REPORTS. Section 8.1(j) is hereby amended by adding
the following new subsection (v):

                  "(v) borrowing base reports substantially in the form of
                  Exhibit X attached hereto on a weekly basis as to the business
                  of ERT and on a monthly basis as to the combined businesses of
                  Cal Dive and Canyon Offshore, with the total Borrowing Base of
                  the Borrower to be brought true with any Accounts no longer
                  meeting the requirements of an Eligible Account on a monthly
                  basis."

         3.03 AMENDMENT TO SECTION 8.2(c). Paragraph (viii) of Section 8.2 (c)
is hereby amended to read as follows:

                  "(viii) plug and abandonment obligations not to exceed
                  $100,000,000 at any time; and"

                                       2
<PAGE>

         3.04 CONSENT TO RESTRICTED INVESTMENT AND ADDITIONAL INDEBTEDNESS.

                  (a)      ERT wishes to acquire

                           (i)      Amerada Hess's interest in the oil and gas
                                    leases in the Gulf of Mexico fields known as
                                    South Marsh Island 130, High Island
                                    A-556/557, Vermilion 331/314, South Marsh
                                    Island 107/114, West Cameron 215, South
                                    Timbalier 213 and West Cameron 277 for a
                                    purchase price not to exceed $15,000,000,
                                    together with the assumption of
                                    approximately $28,000,000 in future plug and
                                    abandonment liability (the "Hess
                                    Acquisition").

                           (ii)     Shell's interest in the oil and gas lease in
                                    the Gulf of Mexico field known as South
                                    Marsh Island 130 for a purchase price not to
                                    exceed $12,200,000, together with the
                                    assumption of approximately $25,000,000 in
                                    future plug and abandonment liability (the
                                    "Shell Acquisition").

                  (b)      The Hess Acquisition and Shell Acquisition would
                           violate the covenants contained in Sections 8.2(c) as
                           to Total Indebtedness and 8.2(r) as to Restricted
                           Investments of the Loan Agreement.

                  (c)      The Lenders hereby waive the requirements of Sections
                           8.2(c) and 8.2(r) in connection with the Hess
                           Acquisition and the Shell Acquisition. The waivers
                           contained in this Section 2.04 shall not serve as a
                           precedent to any future consents, waivers or
                           modifications concerning the Loan Agreement requested
                           by any party, nor bind the Lenders to agree to any
                           other requests by the Borrower for modifications or
                           waivers to any provision of the Loan Agreement or any
                           other Loan Document.

                                   ARTICLE IV
                              CONDITIONS PRECEDENT

         4.01 CONDITIONS TO EFFECTIVENESS. The effectiveness of this Second
Amendment is subject to the satisfaction of the following conditions precedent,
unless specifically waived in writing by the Agent:

                  (a)      The Agent shall have received this Second Amendment,
                           duly executed by each Borrower;

                  (b)      The Agent shall have received a company general
                           certificate from each Borrower certified by the
                           Secretary or Assistant Secretary of each Borrower
                           acknowledging (A) that such Borrower's Board of
                           Directors has adopted, approved, consented to and
                           ratified resolutions which authorize the execution,
                           delivery and performance by such Borrower of this
                           Amendment and all other documents and agreements
                           contemplated herein, and (B) the names of the
                           officers of such Borrower authorized to sign this
                           Second Amendment and all other documents and
                           agreements

                                       3
<PAGE>

                           contemplated herein (including the
                           certificates contemplated herein) together with
                           specimen signatures of such officers;

                  (c)      The representations and warranties contained in this
                           Second Amendment and in the Loan Agreement and the
                           other Loan Documents shall be true and correct as of
                           the date hereof, as if made on the date hereof;

                  (d)      No Default or Event of Default shall have occurred
                           and be continuing, unless such Default or Event of
                           Default has been specifically waived in writing by
                           the Agent; and

                  (e)      All corporate proceedings taken in connection with
                           the transactions contemplated by this Second
                           Amendment and all documents, instruments and other
                           legal matters incident thereto shall be satisfactory
                           to the Agent and its legal counsel.

                                    ARTICLE V
                  RATIFICATIONS, REPRESENTATIONS AND WARRANTIES

         5.01 RATIFICATIONS. The terms and provisions set forth in this Second
Amendment shall modify and supersede all inconsistent terms and provisions set
forth in the Loan Agreement and the other Loan Documents, and, except as
expressly modified and superseded by this Second Amendment, the terms and
provisions of the Loan Agreement and the other Loan Documents are ratified and
confirmed and shall continue in full force and effect. The Borrower, the Agent
and the Lenders agree that the Loan Agreement and the other Loan Documents, as
amended hereby, shall continue to be legal, valid, binding and enforceable in
accordance with their respective terms.

         5.02 REPRESENTATIONS AND WARRANTIES. Each Borrower hereby represents
and warrants to the Agent and the Lenders that (a) the execution, delivery and
performance of this Second Amendment and any and all other Loan Documents
executed or delivered in connection herewith have been authorized by all
requisite corporate action on the part of such Borrower and will not violate the
Articles or Certificate of Incorporation or Bylaws of such Borrower; (b)
presently effective resolutions of such Borrower's Board of Directors authorize
the execution, delivery and performance of this Amendment and any and all other
Loan Documents executed and/or delivered in connection herewith; (c) the
representations and warranties contained in the Loan Agreement, as amended
hereby, and any other Loan Document are true and correct on and as of the date
hereof and on and as of the date of execution hereof as though made on and as of
each such date; (d) no Default or Event of Default under the Loan Agreement, as
amended hereby, has occurred and is continuing, unless such Default or Event of
Default has been specifically waived in writing by the Agent on behalf of the
Lenders; (e) each Borrower is in full compliance with all covenants and
agreements contained in the Loan Agreement and the other Loan Documents, as
amended hereby; and (f) each Borrower has not amended its Articles or
Certificate of Incorporation or its Bylaws since the date of the Loan Agreement,
except for such amendments, if any, which are attached as exhibits to the
certificates referred to in Section 3.01(b) above.

                                       4
<PAGE>

                                   ARTICLE VI
                            MISCELLANEOUS PROVISIONS

         6.01 SURVIVAL OF REPRESENTATIONS AND WARRANTIES. All representations
and warranties made in the Loan Agreement or any other Loan Document, including,
without limitation, any document furnished in connection with this Second
Amendment, shall survive the execution and delivery of this Second Amendment and
the other Loan Documents in accordance with Section 7.3 of the Loan Agreement,
and no investigation by the Agent or Lenders or any closing shall affect the
representations and warranties or the right of the Agent or the Lenders to rely
upon them.

         6.02 REFERENCE TO LOAN DOCUMENTS. Each of the Loan Agreement and the
other Loan Documents, and any and all other agreements, documents or instruments
now or hereafter executed and delivered pursuant to the terms hereof or pursuant
to the terms of the Loan Documents, as amended hereby, are hereby amended so
that any reference in the Loan Agreement and such other Loan Documents to any
other Loan Document shall mean a reference to the Loan Documents as amended
hereby.

         6.03 EXPENSES OF LENDER. As provided in the Loan Agreement, the
Borrower agrees to pay on demand all costs and expenses incurred by the Agent
and the Lenders in connection with the preparation, negotiation, and execution
of this Second Amendment and the other Loan Documents executed pursuant hereto
and any and all amendments, modifications, and supplements thereto, including,
without limitation, the costs and fees of the Agent's legal counsel, and all
costs and expenses incurred by the Agent and the Lenders in connection with the
enforcement or preservation of any rights under the Loan Agreement, as amended
hereby, or any other Loan Document, including, without limitation, the costs and
fees of the Agent's and the Lenders' legal counsel.

         6.04 SEVERABILITY. Any provision of this Second Amendment held by a
court of competent jurisdiction to be invalid or unenforceable shall not impair
or invalidate the remainder of this Amendment and the effect thereof shall be
confined to the provision so held to be invalid or unenforceable.

         6.05 SUCCESSORS AND ASSIGNS. This Second Amendment is binding upon and
shall inure to the benefit of the Agent, the Lenders and the Borrower and their
respective successors and assigns, except that the Borrower may not assign or
transfer any of its rights or obligations hereunder without the prior written
consent of the Agent.

         6.06 COUNTERPARTS. This Second Amendment may be executed in one or more
counterparts, each of which when so executed shall be deemed to be an original,
but all of which when taken together shall constitute one and the same
instrument.

         6.07 EFFECT OF WAIVER. No consent or waiver, express or implied, by the
Agent or Lenders to or for any breach of or deviation from any covenant or
condition by the Borrower shall be deemed a consent to or waiver of any other
breach of the same or any other covenant, condition or duty.

                                       5
<PAGE>

         6.08 HEADINGS. The headings, captions, and arrangements used in this
Second Amendment are for convenience only and shall not affect the
interpretation of this Second Amendment.

         6.09 APPLICABLE LAW. THIS SECOND AMENDMENT SHALL BE DEEMED TO HAVE BEEN
MADE AND TO BE PERFORMABLE IN AND SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE INTERNAL LAWS OF THE STATE OF TEXAS.

         6.10 FINAL AGREEMENT. THE LOAN AGREEMENT AND THE OTHER LOAN DOCUMENTS,
EACH AS AMENDED HEREBY, REPRESENT THE ENTIRE EXPRESSION OF THE PARTIES WITH
RESPECT TO THE SUBJECT MATTER HEREOF ON THE DATE THIS SECOND AMENDMENT IS
EXECUTED. THE LOAN AGREEMENT AND THE OTHER LOAN DOCUMENTS, AS AMENDED HEREBY,
MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR SUBSEQUENT ORAL
AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE
PARTIES. NO MODIFICATION, RESCISSION, WAIVER, RELEASE OR AMENDMENT OF ANY
PROVISION OF THIS SECOND AMENDMENT SHALL BE MADE, EXCEPT BY A WRITTEN AGREEMENT
SIGNED BY BORROWERS AND LENDER.

         6.11 RELEASE. EACH BORROWER HEREBY ACKNOWLEDGES THAT AS OF THE DATE
HEREOF IT HAS NO DEFENSE, COUNTERCLAIM, OFFSET, CROSS-COMPLAINT, CLAIM OR DEMAND
OF ANY KIND OR NATURE WHATSOEVER THAT CAN BE ASSERTED TO REDUCE OR ELIMINATE ALL
OR ANY PART OF ITS LIABILITY TO REPAY THE OBLIGATIONS OR TO SEEK AFFIRMATIVE
RELIEF OR DAMAGES OF ANY KIND OR NATURE FROM THE LENDERS. THE BORROWER HEREBY
VOLUNTARILY AND KNOWINGLY RELEASES AND FOREVER DISCHARGES THE AGENT AND THE
LENDERS, THEIR PREDECESSORS, OFFICERS, DIRECTORS, EMPLOYEES, AGENTS, SUCCESSORS
AND ASSIGNS, FROM ALL POSSIBLE CLAIMS, DEMANDS, ACTIONS, CAUSES OF ACTION,
DAMAGES, COSTS, EXPENSES, AND LIABILITIES WHATSOEVER, KNOWN OR UNKNOWN,
ANTICIPATED OR UNANTICIPATED, SUSPECTED OR UNSUSPECTED, FIXED, CONTINGENT, OR
CONDITIONAL, AT LAW OR IN EQUITY (EXCEPT FOR POSSIBLE CLAIMS, DEMANDS, ACTIONS,
CAUSES OF ACTION, DAMAGES, COSTS, EXPENSES AND LIABILITIES CAUSED BY THE GROSS
NEGLIGENCE OR WILLFUL MISCONDUCT OF THE AGENT OR THE LENDERS, THEIR
PREDECESSORS, AGENTS, EMPLOYEES, SUCCESSORS AND ASSIGNS), ORIGINATING IN WHOLE
OR IN PART ON OR BEFORE THE DATE THIS SECOND AMENDMENT IS EXECUTED, WHICH THE
BORROWER MAY NOW OR HEREAFTER HAVE AGAINST THE AGENT OR THE LENDERS, THEIR
PREDECESSORS, OFFICERS, DIRECTORS, EMPLOYEES, AGENTS, SUCCESSORS AND ASSIGNS),
IF ANY, AND IRRESPECTIVE OF WHETHER ANY SUCH CLAIMS ARISE OUT OF CONTRACT, TORT,
VIOLATION OF LAW OR REGULATIONS, OR OTHERWISE, AND ARISING FROM ANY LOANS,
INCLUDING, WITHOUT LIMITATION, ANY CONTRACTING FOR, CHARGING, TAKING, RESERVING,
COLLECTING OR RECEIVING INTEREST IN EXCESS OF THE HIGHEST LAWFUL RATE
APPLICABLE, THE EXERCISE OF ANY RIGHTS AND REMEDIES

                                       6
<PAGE>

UNDER THE LOAN AGREEMENT OR OTHER LOAN DOCUMENTS, AND NEGOTIATION FOR AND
EXECUTION OF THIS SECOND AMENDMENT.

         IN WITNESS WHEREOF, this Second Amendment has been executed as of
August 30, 2002.

                                       CAL DIVE INTERNATIONAL, INC.

                                       By: /s/ A. WADE PURSELL
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Senior Vice President & CFO

                                       ENERGY RESOURCE TECHNOLOGY, INC.

                                       By: /s/ A. WADE PURSELL
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Senior Vice President & Treasurer

                                       CANYON OFFSHORE, INC.

                                       By: /s/ A. WADE PURSELL
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Vice President & Treasurer

                                       FLEET CAPITAL CORPORATION, as Agent for
                                       the Lenders

                                       By: /s/ E. JAMES BECKEMEIER
                                          --------------------------------------
                                       Name: E. James Beckemeier
                                       Title: Vice President

                                       FLEET CAPITAL CORPORATION

                                       By: /s/ E. JAMES BECKEMEIER
                                          --------------------------------------
                                       Name: E. James Beckemeier
                                       Title: Vice President

                                       7
<PAGE>

                                       SOUTHWEST BANK OF TEXAS, N.A.

                                       By: /s/ PAUL W. COLE
                                          --------------------------------------
                                       Name: Paul W. Cole
                                       Title: Vice President

                                       WHITNEY NATIONAL BANK

                                       By: /s/ HARRY C. STAHEL
                                          --------------------------------------
                                       Name: Harry C. Stahel
                                       Title: Senior Vice President

                                       8
<PAGE>

                         SCHEDULE 1 TO SECOND AMENDMENT

<Table>
<Caption>
Lender                              Portion of Increase in Revolving Credit Commitment
------                              --------------------------------------------------
<S>                                 <C>
Fleet Capital Corporation           USD 4,083,334

Whitney National Bank               USD 2,333,000

Southwest Bank of Texas, N.A.       USD   583,333
</Table><PAGE>
                                                                     EXHIBIT 4.5

   FOURTH AMENDMENT TO SECOND AMENDED AND RESTATED LOAN AND SECURITY AGREEMENT

         THIS FOURTH AMENDMENT TO SECOND AMENDED AND RESTATED LOAN AND SECURITY
AGREEMENT (this "Fourth Amendment") is made and entered into this 14th day of
February, 2003, by and among FLEET CAPITAL CORPORATION, a Rhode Island
corporation (in its individual capacity, "Fleet"), successor in interest by
assignment to Shawmut Capital Corporation ("Shawmut"), SOUTHWEST BANK OF TEXAS,
N.A., a national banking association ("Southwest"); WHITNEY NATIONAL BANK, a
national banking association ("Whitney"); (Fleet, Whitney and Southwest being
referred to herein collectively as the "Lenders"), Fleet as Agent for the
Lenders (the "Agent"); CANYON OFFSHORE, INC. ("Canyon"), a Texas corporation;
CAL DIVE INTERNATIONAL, INC., a Minnesota corporation ("Cal Dive") and ENERGY
RESOURCE TECHNOLOGY, INC., a Delaware corporation ("ERT") (Cal Dive, ERT, and
Canyon being referred to individually and collectively as the "Borrower").

                                    RECITALS

     A. The Borrower, Aquatica, Inc., the Agent and the Lenders entered into
that certain Second Amended and Restated Loan and Security Agreement (as
amended, modified and supplemented from time to time, the "Loan Agreement"),
dated as of February 22, 2002.

     B. The Borrower, Aquatica, Inc., the Agent and the Lenders entered into
that certain First Amendment to Second Amended and Restated Loan and Security
Agreement dated August 9, 2002.

     C. Aquatica, Inc., a Borrower under the Loan Agreement merged with Cal
Dive, with Cal Dive as the surviving entity, pursuant to the Articles of Merger
dated June 27, 2002.

     D. The Borrower, the Agent and the Lenders entered into that certain Second
Amendment to Second Amended and Restated Loan and Security Agreement dated
August 30, 2002.

     E. The Borrower, the Agent and the Lenders entered into that certain Third
Amendment to Second Amended and Restated Loan Agreement dated October 24, 2002.

     F. The Borrower, the Agent and the Lenders have agreed to amend the Loan
Agreement to, among other things, modify the defined terms and to add a new
subsidiary of Cal Dive as a Borrower under the Loan Agreement.

     NOW THEREFORE, in consideration of the premises herein contained and other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties, intending to be legally bound, agree as follows:

                                    ARTICLE I
                                   Definitions

     1.01 Capitalized terms used in this Fourth Amendment are used with the
definitions given to them in the Loan Agreement, as amended hereby, unless
otherwise stated.

                                   ARTICLE II
                                   Amendments

     2.01 Amendments to Defined Terms.

     (a)  The definition of EBIT in Section 1.1 of the Loan Agreement is hereby
          amended to read as follows: "EBIT - means for any period, on a
          Consolidated basis, the sum of the amounts for such period, without
          duplication of: (i) Net Income, plus (ii) charges against income for
          foreign, federal, state and local taxes, to the extent deducted in
          computing Net Income, plus (iii) Interest Expense, plus (iv)
          extraordinary or non-recurring non-cash losses to the extent deducted
          in computing Net Income, minus (v) extraordinary or non-recurring
          non-cash gains to the extent included in computing Net Income;
          provided, however, that a one-time charge in the fourth quarter of
          2002 in an amount not to exceed USD 5,200,000 arising out of the
          settlement of a lawsuit brought by EEX, Inc. against Cal Dive may be
          excluded from the determination of EBIT."

     (b)  The definition of EBITDA in Section 1.1 of the Loan Agreement is
          hereby amended to read as follows: "EBITDA - means, for any period, on
          a Consolidated basis, the sum of the amounts for such period, without
          duplication of (i) Net Income, plus (ii) charges against income for
          foreign, federal, state and local taxes, to the extent deducted in
          computing Net Income, plus (iii) Interest Expense, plus (iv)
          depreciation

<PAGE>

          expense, to the extent deducted in computing Net Income, plus (v)
          amortization expense, including without limitation amortization of
          goodwill, other intangible assets and transaction expenses, to the
          extent deducted in computing Net Income, plus (vi) extraordinary or
          non-recurring non-cash losses to the extent deducted in computing Net
          Income, minus (vii) extraordinary or non-recurring non-cash gains to
          the extent included in computing Net Income; provided, however, that a
          one-time charge in the fourth quarter of 2002 in an amount not to
          exceed USD 5,200,000 arising out of the settlement of a lawsuit
          brought by EEX, Inc. against Cal Dive may be excluded from the
          determination of EBITDA."

     2.02 Addition of Borrower.

     (a) From and after the date of this Fourth Amendment, Well Ops Inc., a
Texas corporation having its chief executive office at 400 N. Sam Houston
Parkway E., Suite 400, Houston, Texas 77060-3500 shall be a Borrower under the
Loan Agreement.

     (b) From and after the date of this Fourth Amendment, all references to the
Borrower in the Loan Agreement shall include Well Ops Inc. and all provisions of
the Loan Agreement affecting the Borrower shall affect Wells Ops Inc.

     (c) The addition of Well Ops Inc. as a Borrower shall be evidenced by the
Amended and Restated Revolving Credit Notes of the Borrower substantially in the
form of Exhibits A-1, A-2 and A-3 attached hereto (the "Restated Notes").

     2.03 Cash Flow Leverage Test. Compliance by the Borrower with the Cash Flow
Leverage Test contained in Section 8.3(a) of the Loan Agreement is hereby waived
for the fourth calendar quarter of 2002 only. The waiver contained in this
Section 2.03 shall not serve as a precedent to any future consents, waivers or
modifications concerning the Loan Agreement requested by any party, nor bind the
Lenders to agree to any other requests by the Borrower for modifications or
waivers to any provision of the Loan Agreement or any other Loan Document.

                                   ARTICLE III
                              Conditions Precedent

     3.01 Conditions to Effectiveness. The effectiveness of this Fourth
Amendment is subject to the satisfaction of the following conditions precedent,
unless specifically waived in writing by the Agent:

     (a) The Agent shall have received this Fourth Amendment and the Restated
Notes, duly executed by each Borrower and Well Ops Inc.;

     (b) The Agent shall have received a certificate from each Borrower
certified by the Secretary or Assistant Secretary of such company acknowledging
(A) that such company's Board of Directors has adopted, approved, consented to
and ratified resolutions which authorize the execution, delivery and performance
by such company of this Fourth Amendment and all other documents and agreements
contemplated herein, and (B) the names of the officers of such company
authorized to sign this Fourth Amendment and all other documents and agreements
contemplated herein (including the certificates contemplated herein) together
with specimen signatures of such officers;

     (c) The Agent shall have received a certificate from the Secretary or
Assistant Secretary of Well Ops Inc. attaching copies of (A) the Articles of
Incorporation and Bylaws of such company, (B) Resolutions of the Board of
Directors of such company authorizing the execution and delivery and performance
of this Fourth Amendment and all other documents and agreements contemplated
herein and (C) the names of the officers of such company authorized to sign this
Fourth Amendment and all other documents contemplated herein together with
specimen signatures of such officers.

     (d) The representations and warranties contained in this Fourth Amendment
and in the Loan Agreement and the other Loan Documents shall be true and correct
as of the date hereof, as if made on the date hereof;

     (e) No Default or Event of Default shall have occurred and be continuing,
unless such Default or Event of Default has been specifically waived in writing
by the Agent; and

     (f) All corporate proceedings taken in connection with the transactions
contemplated by this Fourth Amendment and all documents, instruments and other
legal matters incident thereto shall be satisfactory to the Agent and its legal
counsel.

<PAGE>

                                   ARTICLE IV
                  Ratifications, Representations and Warranties

     4.01 Ratifications. The terms and provisions set forth in this Fourth
Amendment shall modify and supersede all inconsistent terms and provisions set
forth in the Loan Agreement and the other Loan Documents, and, except as
expressly modified and superseded by this Fourth Amendment, the terms and
provisions of the Loan Agreement and the other Loan Documents are ratified and
confirmed and shall continue in full force and effect. The Borrower, the Agent
and the Lenders agree that the Loan Agreement and the other Loan Documents, as
amended by this Fourth Amendment, shall continue to be legal, valid, binding and
enforceable in accordance with their respective terms.

     4.02 Representations and Warranties. Each Borrower and Well Ops Inc. hereby
represents and warrants to the Agent and the Lenders that (a) the execution,
delivery and performance of this Fourth Amendment and any and all other Loan
Documents executed or delivered in connection herewith have been authorized by
all requisite corporate action on the part of such company and will not violate
the Articles or Certificate of Incorporation or Bylaws of such company; (b)
presently effective resolutions of such company's Board of Directors authorize
the execution, delivery and performance of this Fourth Amendment and any and all
other Loan Documents executed and/or delivered in connection herewith; (c) the
representations and warranties contained in the Loan Agreement, as amended by
this Fourth Amendment, and any other Loan Document are true and correct on and
as of the date hereof and on and as of the date of execution hereof as though
made on and as of each such date; (d) no Default or Event of Default under the
Loan Agreement, as amended by this Fourth Amendment, has occurred and is
continuing, unless such Default or Event of Default has been specifically waived
in writing by the Agent on behalf of the Lenders; (e) each Borrower and Well Ops
Inc. is in full compliance with all covenants and agreements contained in the
Loan Agreement and the other Loan Documents, as amended by this Fourth
Amendment; and (f) no Borrower has amended its Articles or Certificate of
Incorporation or its Bylaws since the date of the Loan Agreement, except for
such amendments, if any, which are attached as exhibits to the certificates
referred to in Section 3.01(b) above.

                                    ARTICLE V
                            Miscellaneous Provisions

     5.01 Survival of Representations and Warranties. All representations and
warranties made in the Loan Agreement or any other Loan Document, including,
without limitation, any document furnished in connection with this Fourth
Amendment, shall survive the execution and delivery of this Fourth Amendment and
the other Loan Documents in accordance with Section 7.3 of the Loan Agreement,
and no investigation by the Agent or the Lenders or any closing shall affect the
representations and warranties or the right of the Agent or the Lenders to rely
upon them.

     5.02 Reference to Loan Documents. Each of the Loan Agreement and the other
Loan Documents, and any and all other agreements, documents or instruments now
or hereafter executed and delivered pursuant to the terms hereof or pursuant to
the terms of the Loan Documents, as amended hereby, are hereby amended so that
any reference in the Loan Agreement and such other Loan Documents to any other
Loan Document shall mean a reference to the Loan Documents as amended by this
Fourth Amendment.

     5.03 Expenses of Lender. As provided in the Loan Agreement, the Borrower
agrees to pay on demand all costs and expenses incurred by the Agent and the
Lenders in connection with the preparation, negotiation, and execution of this
Fourth Amendment and the other Loan Documents executed pursuant hereto and any
and all amendments, modifications, and supplements thereto, including, without
limitation, the costs and fees of the Agent's legal counsel, and all costs and
expenses incurred by the Agent and the Lenders in connection with the
enforcement or preservation of any rights under the Loan Agreement, as amended
by this Fourth Amendment, or any other Loan Document, including, without
limitation, the costs and fees of the Agent's and the Lenders' legal counsel.

     5.04 Severability. Any provision of this Fourth Amendment held by a court
of competent jurisdiction to be invalid or unenforceable shall not impair or
invalidate the remainder of this Fourth Amendment and the effect thereof shall
be confined to the provision so held to be invalid or unenforceable.

<PAGE>

     5.05 Successors and Assigns. This Fourth Amendment is binding upon and
shall inure to the benefit of the Agent, the Lenders and the Borrower and their
respective successors and assigns, except that the Borrower may not assign or
transfer any of its rights or obligations hereunder without the prior written
consent of the Agent.

     5.06 Counterparts. This Fourth Amendment may be executed in one or more
counterparts, each of which when so executed shall be deemed to be an original,
but all of which when taken together shall constitute one and the same
instrument.

     5.07 Effect of Waiver. No consent or waiver, express or implied, by the
Agent or the Lenders to or for any breach of or deviation from any covenant or
condition by the Borrower shall be deemed a consent to or waiver of any other
breach of the same or any other covenant, condition or duty.

     5.08 Headings. The headings, captions, and arrangements used in this Fourth
Amendment are for convenience only and shall not affect the interpretation of
this Fourth Amendment.

     5.09 Applicable Law. THIS FOURTH AMENDMENT SHALL BE DEEMED TO HAVE BEEN
MADE AND TO BE PERFORMABLE IN AND SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE INTERNAL LAWS OF THE STATE OF TEXAS.

     5.10 Final Agreement. THE LOAN AGREEMENT AND THE OTHER LOAN DOCUMENTS, EACH
AS AMENDED BY THIS FOURTH AMENDMENT, REPRESENT THE ENTIRE EXPRESSION OF THE
PARTIES WITH RESPECT TO THE SUBJECT MATTER HEREOF ON THE DATE THIS FOURTH
AMENDMENT IS EXECUTED. THE LOAN AGREEMENT AND THE OTHER LOAN DOCUMENTS, AS
AMENDED BY THIS FOURTH AMENDMENT MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR,
CONTEMPORANEOUS OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES. THERE ARE NO
UNWRITTEN ORAL AGREEMENTS BETWEEN THE PARTIES. NO MODIFICATION, RESCISSION,
WAIVER, RELEASE OR AMENDMENT OF ANY PROVISION OF THIS FOURTH AMENDMENT SHALL BE
MADE, EXCEPT BY A WRITTEN AGREEMENT SIGNED BY THE BORROWER AND THE LENDERS.

     5.11 Release. EACH BORROWER HEREBY ACKNOWLEDGES THAT AS OF THE DATE HEREOF
IT HAS NO DEFENSE, COUNTERCLAIM, OFFSET, CROSS-COMPLAINT, CLAIM OR DEMAND OF ANY
KIND OR NATURE WHATSOEVER THAT CAN BE ASSERTED TO REDUCE OR ELIMINATE ALL OR ANY
PART OF ITS LIABILITY TO REPAY THE OBLIGATIONS OR TO SEEK AFFIRMATIVE RELIEF OR
DAMAGES OF ANY KIND OR NATURE FROM THE LENDERS. THE BORROWER HEREBY VOLUNTARILY
AND KNOWINGLY RELEASES AND FOREVER DISCHARGES THE AGENT AND THE LENDERS, THEIR
PREDECESSORS, OFFICERS, DIRECTORS, EMPLOYEES, AGENTS, SUCCESSORS AND ASSIGNS,
FROM ALL POSSIBLE CLAIMS, DEMANDS, ACTIONS, CAUSES OF ACTION, DAMAGES, COSTS,
EXPENSES, AND LIABILITIES WHATSOEVER, KNOWN OR UNKNOWN, ANTICIPATED OR
UNANTICIPATED, SUSPECTED OR UNSUSPECTED, FIXED, CONTINGENT, OR CONDITIONAL, AT
LAW OR IN EQUITY (EXCEPT FOR POSSIBLE CLAIMS, DEMANDS, ACTIONS, CAUSES OF
ACTION, DAMAGES, COSTS, EXPENSES AND LIABILITIES CAUSED BY THE GROSS NEGLIGENCE
OR WILLFUL MISCONDUCT OF THE AGENT OR THE LENDERS, THEIR PREDECESSORS, AGENTS,
EMPLOYEES, SUCCESSORS AND ASSIGNS), ORIGINATING IN WHOLE OR IN PART ON OR BEFORE
THE DATE THIS FOURTH AMENDMENT IS EXECUTED, WHICH THE BORROWER MAY NOW OR
HEREAFTER HAVE AGAINST THE AGENT OR THE LENDERS, THEIR PREDECESSORS, OFFICERS,
DIRECTORS, EMPLOYEES, AGENTS, SUCCESSORS AND ASSIGNS), IF ANY, AND IRRESPECTIVE
OF WHETHER ANY SUCH CLAIMS ARISE OUT OF CONTRACT, TORT, VIOLATION OF LAW OR
REGULATIONS, OR OTHERWISE, AND ARISING FROM ANY LOANS, INCLUDING, WITHOUT
LIMITATION, ANY CONTRACTING FOR, CHARGING, TAKING, RESERVING, COLLECTING OR
RECEIVING INTEREST IN EXCESS OF THE HIGHEST LAWFUL RATE APPLICABLE, THE EXERCISE
OF ANY RIGHTS AND REMEDIES UNDER THE LOAN AGREEMENT OR OTHER LOAN DOCUMENTS, AND
NEGOTIATION FOR AND EXECUTION OF THIS FOURTH AMENDMENT.

<PAGE>

IN WITNESS WHEREOF, this Fourth Amendment has been executed as of February 14,
2003.

                                       CAL DIVE INTERNATIONAL, INC.

                                       By: /s/ A. WADE PURSELL
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Senior Vice President and Chief
                                              Financial Officer

                                       ENERGY RESOURCE TECHNOLOGY, INC.

                                       By: /s/ A. WADE PURSELL
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Senior Vice President and
                                              Treasurer

                                       CANYON OFFSHORE, INC.

                                       By: /s/ A. WADE PURSELL
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Vice President and Treasurer

                                       WELL OPS INC.

                                       By: /s/ A. WADE PURSELL
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Vice President and Treasurer

                                       FLEET CAPITAL CORPORATION,
                                       as Agent for the Lenders

                                       By: /s/ HANCE VANBEBER
                                          --------------------------------------
                                       Name: Hance VanBeber
                                       Title: Senior Vice President

                                       FLEET CAPITAL CORPORATION

                                       By: /s/ HANCE VANBEBER
                                          --------------------------------------
                                       Name: Hance VanBeber
                                       Title: Senior Vice President

                                       SOUTHWEST BANK OF TEXAS, N.A.

                                       By: /s/ PAUL W. COLE
                                          --------------------------------------
                                       Name: Paul W. Cole
                                       Title: Vice President

                                       WHITNEY NATIONAL BANK

                                       By: /s/ HARRY C. STAHEL
                                          --------------------------------------
                                       Name: Harry C. Stahel
                                       Title: Senior Vice President

<PAGE>

                                                                     EXHIBIT A-1
                   AMENDED AND RESTATED REVOLVING CREDIT NOTE

$39,000,000.00                                                 February 14, 2003
                                                                  Houston, Texas

     FOR VALUE RECEIVED, the undersigned (hereinafter referred to collectively
as "Borrower"), hereby PROMISES TO PAY to the order of FLEET CAPITAL
CORPORATION, a Rhode Island corporation ("Lender"), or its registered assigns,
at the office of Fleet Capital Corporation, as Agent for such Lender, or at such
other place in the United States of America as the holder of this Note may
designate from time to time in writing, in lawful money of the United States of
America and in immediately available funds, the principal amount of THIRTY-NINE
MILLION AND NO/100 Dollars ($39,000,000.00), or such lesser principal amount as
may be outstanding pursuant to the Loan Agreement (as hereinafter defined) with
respect to the Revolving Credit Loan, together with interest on the unpaid
principal amount of this Note outstanding from time to time.

     This Note is one of the Notes referred to in, and issued pursuant to, that
certain Second Amended and Restated Loan and Security Agreement dated as of
February 22, 2002, as amended, by and among Borrower, the lenders signatory
thereto (including Lender) and Fleet Capital Corporation ("FCC"), as agent for
such Lenders (FCC in such capacity, the "Agent") (as amended, modified or
restated, from time to time, the "Loan Agreement"), and is entitled to all of
the benefits and security of the Loan Agreement. All of the terms, covenants and
conditions of the Loan Agreement and the other Loan Documents are hereby made a
part of this Note and are deemed incorporated herein in full. All capitalized
terms herein, unless otherwise defined, unless otherwise specifically defined in
this Note, shall have the meanings ascribed to them in the Loan Agreement.

     The principal amount of the indebtedness evidenced hereby shall be payable
in the amounts and on the dates specified in the Loan Agreement and, if not
sooner paid in full, on the last day of the Term, unless the term hereof is
extended in accordance with the Loan Agreement. Interest thereon shall be paid
until such principal amount is paid in full at such interest rates and at such
times as are specified in the Loan Agreement. Upon and after the occurrence, and
during the continuation, of an Event of Default, this Note shall or may, as
provided in the Loan Agreement, become or be declared immediately due and
payable. The right to receive principal of, and stated interest on, this Note
may only be transferred in accordance with the provisions of the Loan Agreement.

     Demand, presentment, protest and notice of nonpayment and protest are
hereby waived by Borrower.

     This Note is the amendment, restatement, renewal and extension of the
promissory note of the Borrower dated October 24, 2002.

     This Note shall be interpreted, governed by, and construed in accordance
with, the internal laws of the State of Texas.

                                       CAL DIVE INTERNATIONAL, INC.,
                                       a Minnesota corporation
                                       By:
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Senior Vice President and Chief
                                              Financial Officer

                                       ENERGY RESOURCE TECHNOLOGY, INC.,
                                       a Delaware corporation
                                       By:
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Senior Vice President and
                                              Treasurer

                                       CANYON OFFSHORE, INC., a Texas
                                       corporation
                                       By:
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Vice President and Treasurer

                                       WELL OPS INC., a Texas corporation
                                       By:
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Vice President and Treasurer

<PAGE>

                                                                     EXHIBIT A-2
                   AMENDED AND RESTATED REVOLVING CREDIT NOTE

$25,000,000.00                                                 February 14, 2003
                                                                  Houston, Texas

     FOR VALUE RECEIVED, the undersigned (hereinafter referred to collectively
as "Borrower"), hereby PROMISES TO PAY to the order of WHITNEY NATIONAL BANK, a
national banking association ("Lender"), or its registered assigns, at the
office of Fleet Capital Corporation, as Agent for such Lender, or at such other
place in the United States of America as the holder of this Note may designate
from time to time in writing, in lawful money of the United States of America
and in immediately available funds, the principal amount of TWENTY-FIVE MILLION
AND NO/100 Dollars ($25,000,000.00), or such lesser principal amount as may be
outstanding pursuant to the Loan Agreement (as hereinafter defined) with respect
to the Revolving Credit Loan, together with interest on the unpaid principal
amount of this Note outstanding from time to time.

     This Note is one of the Notes referred to in, and issued pursuant to, that
certain Second Amended and Restated Loan and Security Agreement dated as of
February 22, 2002, as amended, by and among Borrower, the lenders signatory
thereto (including Lender) and Fleet Capital Corporation ("FCC"), as agent for
such Lenders (FCC in such capacity, the "Agent") (as amended, modified or
restated, from time to time, the "Loan Agreement"), and is entitled to all of
the benefits and security of the Loan Agreement. All of the terms, covenants and
conditions of the Loan Agreement and the other Loan Documents are hereby made a
part of this Note and are deemed incorporated herein in full. All capitalized
terms herein, unless otherwise defined, unless otherwise specifically defined in
this Note, shall have the meanings ascribed to them in the Loan Agreement.

     The principal amount of the indebtedness evidenced hereby shall be payable
in the amounts and on the dates specified in the Loan Agreement and, if not
sooner paid in full, on the last day of the Term, unless the term hereof is
extended in accordance with the Loan Agreement. Interest thereon shall be paid
until such principal amount is paid in full at such interest rates and at such
times as are specified in the Loan Agreement.

     Upon and after the occurrence, and during the continuation, of an Event of
Default, this Note shall or may, as provided in the Loan Agreement, become or be
declared immediately due and payable.

     The right to receive principal of, and stated interest on, this Note may
only be transferred in accordance with the provisions of the Loan Agreement.

     Demand, presentment, protest and notice of nonpayment and protest are
hereby waived by Borrower.

     This Note is the amendment, restatement, renewal and extension of the
promissory note of the Borrower dated October 24, 2002.

     This Note shall be interpreted, governed by, and construed in accordance
with, the internal laws of the State of Texas.

                                       CAL DIVE INTERNATIONAL, INC.,
                                       a Minnesota corporation
                                       By:
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Senior Vice President and Chief
                                              Financial Officer

                                       ENERGY RESOURCE TECHNOLOGY, INC.,
                                       a Delaware corporation
                                       By:
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Senior Vice President and
                                              Treasurer

                                       CANYON OFFSHORE, INC., a Texas
                                       corporation
                                       By:
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Vice President and Treasurer

                                       WELL OPS INC., a Texas corporation
                                       By:
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Vice President and Treasurer

<PAGE>

                                                                     EXHIBIT A-3
                   AMENDED AND RESTATED REVOLVING CREDIT NOTE

$6,000,000.00                                                  February 14, 2003
                                                                  Houston, Texas

     FOR VALUE RECEIVED, the undersigned (hereinafter referred to collectively
as "Borrower"), hereby PROMISES TO PAY to the order of SOUTHWEST BANK OF TEXAS,
N.A., a national banking association ("Lender"), or its registered assigns, at
the office of Fleet Capital Corporation, as Agent for such Lender, or at such
other place in the United States of America as the holder of this Note may
designate from time to time in writing, in lawful money of the United States of
America and in immediately available funds, the principal amount of SIX MILLION
AND NO/100 Dollars ($6,000,000.00), or such lesser principal amount as may be
outstanding pursuant to the Loan Agreement (as hereinafter defined) with respect
to the Revolving Credit Loan, together with interest on the unpaid principal
amount of this Note outstanding from time to time.

     This Note is one of the Notes referred to in, and issued pursuant to, that
certain Second Amended and Restated Loan and Security Agreement dated as of
February 22, 2002, as amended, by and among Borrower, the lenders signatory
thereto (including Lender) and Fleet Capital Corporation ("FCC"), as agent for
such Lenders (FCC in such capacity, the "Agent") (as amended, modified or
restated, from time to time, the "Loan Agreement"), and is entitled to all of
the benefits and security of the Loan Agreement. All of the terms, covenants and
conditions of the Loan Agreement and the other Loan Documents are hereby made a
part of this Note and are deemed incorporated herein in full. All capitalized
terms herein, unless otherwise defined, unless otherwise specifically defined in
this Note, shall have the meanings ascribed to them in the Loan Agreement.

     The principal amount of the indebtedness evidenced hereby shall be payable
in the amounts and on the dates specified in the Loan Agreement and, if not
sooner paid in full, on the last day of the Term, unless the term hereof is
extended in accordance with the Loan Agreement. Interest thereon shall be paid
until such principal amount is paid in full at such interest rates and at such
times as are specified in the Loan Agreement.

     Upon and after the occurrence, and during the continuation, of an Event of
Default, this Note shall or may, as provided in the Loan Agreement, become or be
declared immediately due and payable.

     The right to receive principal of, and stated interest on, this Note may
only be transferred in accordance with the provisions of the Loan Agreement.

     Demand, presentment, protest and notice of nonpayment and protest are
hereby waived by Borrower.

     This Note is the amendment, restatement, renewal and extension of the
promissory note of the Borrower dated October 24, 2002.

     This Note shall be interpreted, governed by, and construed in accordance
with, the internal laws of the State of Texas.

                                       CAL DIVE INTERNATIONAL, INC.,
                                       a Minnesota corporation
                                       By:
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Senior Vice President and Chief
                                              Financial Officer

                                       ENERGY RESOURCE TECHNOLOGY, INC.,
                                       a Delaware corporation
                                       By:
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Senior Vice President and
                                              Treasurer

                                       CANYON OFFSHORE, INC., a Texas
                                       corporation
                                       By:
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Vice President and Treasurer

                                       WELL OPS INC., a Texas corporation
                                       By:
                                          --------------------------------------
                                       Name: A. Wade Pursell
                                       Title: Vice President and Treasurer

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