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                                                                   Exhibit 10.07


                                SECOND AMENDMENT
                                       TO
                           SECOND AMENDED AND RESTATED
                 UNDERWRITING AND CONTINUING INDEMNITY AGREEMENT



                  THIS SECOND AMENDMENT TO SECOND AMENDED AND RESTATED
UNDERWRITING AND CONTINUING INDEMNITY AGREEMENT dated as of April 24, 2001 (the
"AMENDMENT") is entered into by and among (i) GREAT LAKES DREDGE & DOCK
CORPORATION, a Delaware corporation ("HOLDINGS"), and the SUBSIDIARIES of
HOLDINGS signatories hereto (collectively with HOLDINGS, the "INDEMNITORS"), and
(ii) RELIANCE INSURANCE COMPANY, a Pennsylvania corporation, UNITED PACIFIC
INSURANCE COMPANY, a Pennsylvania corporation, RELIANCE NATIONAL INSURANCE
COMPANY, a Delaware corporation, and RELIANCE SURETY COMPANY, a Delaware
corporation (collectively, the foregoing parties are referred to herein as
"RELIANCE").

                                   WITNESSETH:

                  WHEREAS, the INDEMNITORS and RELIANCE are parties to a certain
Second Amended and Restated Underwriting and Continuing Indemnity Agreement
dated as of August 19, 1998 (the "AGREEMENT");

                  WHEREAS, in connection with the proposed acquisition by
HOLDNGS of 80% of the equity interests of NORTH AMERICAN SITE DEVELOPERS, INC.,
a Massachusetts corporation ("NASDI"), (i) HOLDINGS will issue additional Debt
(as such term is defined in the Agreement) in an aggregate principal amount of
$40,000,000 pursuant to the terms of the 1998 Debt Indenture (as such term is
defined in the Agreement), (ii) NASDI will issue promissory notes in an
aggregate principal amount equal to $3,000,000 to management stockholders of
NASDI, which promissory notes will be guaranteed by HOLDINGS, and (iii) NASDI
will issue a promissory note in an aggregate principal amount equal to
approximately $32,000,000 to HOLDINGS;

                  WHEREAS, the INDEMNITORS have requested RELIANCE to consent
to, and to amend certain provisions of the Agreement to permit, such
acquisition, such incurrence of additional Debt and such issuance of promissory
notes; and

                  WHEREAS, RELIANCE is willing to amend certain provisions of
the Agreement and to consent to such acquisition, such incurrence of additional
Debt and such issuance of promissory notes, subject to the terms and conditions
set forth herein.

                  NOW, THEREFORE, in consideration of the premises, and
intending to be legally bound hereby, the INDEMNITORS and RELIANCE hereby agree
as follows:

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                  SECTION 1.  CONSENT TO INCURRENCE OF ADDITIONAL DEBT.
RELIANCE hereby consents:

                   (a) to HOLDING'S incurrence of additional Debt in a principal
         amount not to exceed $40,000,000, PROVIDED, HOWEVER, that (i) such
         incurrence of Debt shall be pursuant to the terms of the 1998 Debt
         Indenture, (ii) an amount not to exceed $35,000,000 from the proceeds
         received by HOLDINGS in connection with the incurrence of such Debt
         shall be used by HOLDINGS to acquire 80% of the equity interests of
         NASDI, and (iii) an amount not to exceed $5,000,000 from the proceeds
         received by HOLDINGS in connection with the incurrence of such Debt
         shall be used by HOLDINGS to pay fees and expenses in connection with
         such acquisition and to repay a portion of HOLDING'S outstanding
         revolving loan balance under the Bank Loan Facility (as defined in the
         Underwriting Agreement); and

                  (b) pursuant to Section 6.21 of the Agreement, to HOLDING'S
         modifying the 1998 Debt Indenture to evidence the incurrence of such
         additional Debt pursuant to the existing terms of the 1998 Debt
         Indenture.

                  SECTION 2.  AMENDMENTS TO AGREEMENT.

                  Subject to satisfaction of the conditions set forth in SECTION
2 of this Amendment and in reliance on the INDEMNITORS' warranties set forth in
SECTION 3 below, the Agreement is hereby amended as follows:

                  (a) The definition of "Limited Subsidiary" in Section 1.1 of
         the Agreement is amended by deleting the proviso at the end thereof in
         its entirety and inserting in lieu thereof:

                  "PROVIDED, that none of NATCO Limited Partnership, North
         American TrailingCompany or North

                  American Site Developers, Inc. shall be deemed to be a LIMITED
         SUBSIDIARY for purposes of this Agreement."

                  (b) Section 3.1 of the Agreement is amended by adding the
         language "(other than North American Site Developers, Inc.)"
         immediately after the language "Notwithstanding anything to the
         contrary herein, any INDEMNITOR which is not a wholly-owned SUBSIDIARY
         of HOLDINGS" that appears in such Section.

                  (c) Section 3.2 of the Agreement is amended by adding the
         language "(other than North American Site Developers, Inc.)"
         immediately after the language "Notwithstanding anything to the
         contrary herein, any INDEMNITOR which is not a wholly-owned SUBSIDIARY
         of HOLDINGS" that appears in such Section.

                  (d) Section 6.12(f)(ii) of the Agreement is amended by
         deleting the reference therein to "$115,000,000" and inserting in lieu
         thereof "$155,000,000".

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                  (e) Section 6.12(r) of the Agreement is deleted in its
         entirety and the following inserted in lieu thereof:

                  "(r)     DEBT of North American Site Developers, Inc. owing to
                           management stockholders of North American Site
                           Developers, Inc., PROVIDED, that the aggregate amount
                           of such DEBT shall not exceed at any time the lesser
                           of (i) $3,000,000 and (ii) the aggregate principal
                           amount scheduled to be outstanding at such time in
                           accordance with the terms of those certain promissory
                           notes dated April 24, 2001 from North American Site
                           Developers, Inc. to the order of such management
                           stockholders;"

                  (f) Section 6.13(b) of the Agreement is amended by (i)
         deleting the word "and" that appears immediately prior to subsection
         (iii) of such Section and (ii) by adding the following at the end of
         such Section:

                  ", and (iv) shares of capital stock or equity interests issued
                  by North American Site Developers, Inc. to Persons other than
                  HOLDINGS or a wholly-owned SUBSIDIARY of HOLDINGS, PROVIDED,
                  that the aggregate amount of such shares of capital stock or
                  equity interests issued to such Persons shall not exceed
                  twenty-five percent (25%) of the aggregate number of shares of
                  capital stock or equity interests issued by North American
                  Site Developers, Inc.;"

                  (g)  Section 6.15(e) of the Agreement is amended by adding the
         following at the end thereof:

                  ", and PROVIDED FURTHER, that HOLDINGS or the appropriate
                  SUBSIDIARY will provide RELIANCE with prior written notice of
                  any investment, DEBT or CONTINGENT LIABILITY (other than an
                  investment, DEBT or CONTINGENT LIABILITY made in the ordinary
                  course of business consistent with past business practices) to
                  be made by HOLDINGS or such SUBSIDIARY in NATCO, North
                  American or any SUBSIDIARY thereof;"

                  (h)  Section 6.18 of the Agreement is amended by adding at the
         end thereof the following:

                  ", including, without limitation, the provision of
                  commercial and industrial demolition services."

                  SECTION 3.  CONDITIONS PRECEDENT.

                  This Amendment shall be effective upon receipt by RELIANCE of
the documents listed below, each, unless otherwise noted, dated the date hereof,
duly executed, in form and substance satisfactory to RELIANCE and in quantities
designated by RELIANCE:

                  (a)  This Amendment executed by all parties hereto.

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                  (b) The INDEMNITORS shall have delivered such other documents
         as RELIANCE may reasonably request.

                  SECTION 4.  WARRANTIES.

                  To induce RELIANCE to enter into this Amendment, the
INDEMNITORS warrant to RELIANCE as of the date hereof and after giving effect to
this Amendment that:

                  (a)  The representations and warranties contained in Article V
         of the Agreement, in Section 4 of each SECURITY AGREEMENT (A/R), in
         Section 4 of each SECURITY AGREEMENT (EQUIPMENT), in Section 4 of the
         PLEDGE AGREEMENT and in Article I of each of the VESSEL MORTGAGES, are
         correct in all material respects on and as of the date hereof as though
         made on and as of such date except to the extent stated to relate to an
         earlier date, in which case such representation and warranty shall be
         correct as of such earlier date; and

                  (b)  No EVENT OF DEFAULT has occurred and is continuing.

                  SECTION 5.  GENERAL.

                  (a)  Terms used but not otherwise defined herein are used
         herein as defined in the Agreement.

                  (b)  As hereby modified, the Agreement shall remain in full
         force and effect and is hereby ratified, approved and confirmed in all
         respects.

                  (c)  This Amendment shall be binding upon and shall inure to
         the benefit of the INDEMNITORS and RELIANCE and respective successors
         and assigns of RELIANCE.

                  (d)  This Amendment may be executed in any number of
         counterparts and by the different parties on separate counterparts, and
         each such counterpart shall be deemed to be an original, but all such
         counterparts shall together constitute but one and the same Amendment.



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                  IN WITNESS WHEREOF, this Agreement is executed by the parties
on the day and date first set forth above.

                                     GREAT LAKES DREDGE & DOCK CORPORATION

                                     By: /s/ Deborah A. Wensel
                                        ----------------------------------------
                                     Its:    Vice President and CFO


                                     GREAT LAKES DREDGE & DOCK COMPANY

                                     By: /s/ Deborah A. Wensel
                                        ----------------------------------------
                                     Its:    Vice President and CFO


                                     LYDON DREDGING & CONSTRUCTION COMPANY, LTD.

                                     By: /s/ Deborah A. Wensel
                                        ----------------------------------------
                                     Its:    Vice President and CFO


                                     NATCO DREDGING LIMITED PARTNERSHIP

                                     By: /s/ Deborah A. Wensel
                                        ----------------------------------------
                                     Its:    Vice President

                                     NORTH AMERICAN TRAILING COMPANY

                                     By: /s/ Deborah A. Wensel
                                        ----------------------------------------
                                     Its:    Vice President and CFO


                                     FIFTY-THREE DREDGING COMPANY

                                     By:
                                        ----------------------------------------
                                     Its:    Vice President


                                     DAWSON DREDGING COMPANY

                                     By: /s/ Deborah A. Wensel
                                        ----------------------------------------
                                     Its:    Vice President and CFO
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                  IN WITNESS WHEREOF, this Agreement is executed by the parties
on the day and date first set forth above.


                                     GREAT LAKES DREDGE & DOCK CORPORATION

                                     By:
                                        ----------------------------------------
                                     Its:
                                          --------------------------------------


                                     GREAT LAKES DREDGE & DOCK COMPANY

                                     By:
                                        ----------------------------------------
                                     Its:
                                          --------------------------------------


                                     LYDON DREDGING & CONSTRUCTION COMPANY, LTD.

                                     By:
                                        ----------------------------------------
                                     Its:
                                         ---------------------------------------


                                     NATCO DREDGING LIMITED PARTNERSHIP

                                     By:
                                        ----------------------------------------
                                     Its:
                                         ---------------------------------------


                                     NORTH AMERICAN TRAILING COMPANY

                                     By:
                                        ----------------------------------------
                                     Its:
                                         ---------------------------------------


                                     FIFTY-THREE DREDGING COMPANY

                                     By:  /s/  Paul Dinquel
                                        ----------------------------------------
                                     Its:      Vice President
                                         ---------------------------------------


                                     DAWSON DREDGING COMPANY

                                     By:
                                        ----------------------------------------
                                     Its:
                                         ---------------------------------------

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                                     GREAT LAKES CARIBBEAN DREDGING, INC.

                                     By: /s/ Deborah A. Wensel
                                        ----------------------------------------
                                     Its: Vice President and CFO
                                         ---------------------------------------


                                     NORTH AMERICAN SITE DEVELOPERS, INC.

                                     By: /s/ Deborah A. Wensel
                                        ----------------------------------------
                                     Its: Vice President
                                         ---------------------------------------


                                     RELIANCE INSURANCE COMPANY
                                     UNITED PACIFIC INSURANCE COMPANY
                                     RELIANCE NATIONAL INSURANCE COMPANY
                                     RELIANCE SURETY COMPANY

                                     By:      /s/
                                        ----------------------------------------

                                     Its:     Attorney-in-Fact
                                         ---------------------------------------