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                THIRD AMENDMENT TO CREDIT AND SECURITY AGREEMENT

PREAMBLE. This Third Amendment to Credit and Security Agreement (this
"Amendment") dated as of October 22, 2004, is made among (i) OMNI ENERGY
SERVICES CORP., a Louisiana corporation "Parent Company"); AMERICAN HELICOPTERS
INC., a Texas corporation ("AHT"); and OMNI ENERGY SERVICES CORP.-MEXICO, a
Louisiana corporation ("Mexico"; Mexico, AHI and Parent Company herein sometimes
called individually, "Initial Borrower" and, collectively, the "Initial
Borrowers"); (ii) TRUSSCO, INC., a Louisiana corporation ("Trussco") and TRUSSCO
PROPERTIES, LLC, a Louisiana limited liability company ("Trussco Properties";
Trussco Properties and Trussco herein sometimes called, individually, "New
Borrower" and, collectively, the "New Borrowers"; each New Borrower and each
Initial Borrower herein sometimes called, individually, a "Borrower" and,
collectively, the "Borrowers"); and (iii) WEBSTER BUSINESS CREDIT CORPORATION, a
corporation organized under the laws of the State of New York ("WBCC"),
individually, as lender hereunder and as agent for itself and each other Lender
Party (as hereinafter defined) (WBCC, acting in both such capacities, herein
called "Lender"), for the purpose of amending further the Credit and Security
Agreement, dated December 23, 2003, between Borrowers and Lender, as amended to
date (the "Credit Agreement"), in order to reflect, among other things, (i) the
incurrence by the Borrowers of certain new Indebtedness from another lender,
consisting of a bridge loan in the principal amount of $6,500,000, (ii) the full
prepayment of the existing Term Loan in connection therewith, and (iii) the
release of certain Collateral by Lender to be used to secure the payment of the
new Indebtedness.

      1.  Definitions. Capitalized terms used in this Amendment, but not
expressly defined herein, shall have the same meanings as given to such terms in
the Credit Agreement.

      2.  Amendments.

            2.1.  Definitions. The following new definitions shall be added to
Annex One of the Credit Agreement in the correct alphabetical order:

                  "Bridge Lender" shall mean Beal Bank, S.S.B., its successors
            and assigns.

                  "Bridge Loan" shall mean the loan of $6,500,000 in principal
            amount to be made by the Bridge Lender to Borrowers pursuant to the
            Bridge Loan Agreement plus fees, expenses and interest.

                  "Bridge Loan Agreement" shall mean the collective reference to
            (i) the Promissory Note, (ii) the Assignment of Account and Security
            Agreement, and (iii) the Security Agreement, each dated as of
            October 22, 2004, made between Bridge Lender and Borrower, as each
            may be amended or modified from time to time consistent with Section
            7.15 hereof.

                  "Bridge Loan Amendment" shall mean the Third Amendment to
            Credit and Security Agreement, dated as of October 22, 2004, made
            between Lender and Borrowers, amending the Agreement.

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                  "Bridge Loan Documents" shall mean, collectively, (i) the
            Bridge Loan Agreement, and (ii) all other documents, instruments and
            agreements executed by Borrowers with or in favor of Bridge Lender
            in connection therewith.

                  "Bridge Loan Lien" shall mean the Lien of Bridge Lender on the
            Bridge Loan Lien Property securing payment of the Bridge Loan.

                  "Bridge Loan Lien Property" shall mean the assets and
            properties of Borrowers set forth and described on Schedule "1" to
            the Bridge Loan Amendment.

            2.2.  Bridge Loan. Lender hereby consents to the incurrence by
Borrowers of the Bridge Loan and the granting by Borrowers of the Bridge Loan
Lien on the Bridge Loan Lien Property pursuant to the Bridge Loan Documents,
such that, henceforth; (i) the Bridge Loan shall constitute permitted
Indebtedness under Section 7.9 of the Credit Agreement; (ii) the Bridge Loan
Lien, to the extent it secures payment of the Bridge Loan, shall constitute a
Permitted Encumbrance; (iii) the Bridge Loan Lien Property shall constitute
Excluded Equipment; and (iv) the Bridge Loan Documents shall constitute Material
Agreements. Further in regard to the foregoing, Lender hereby releases its Liens
on all Collateral consisting of, and limited to, the Bridge Loan Lien Property
and agrees to amend of record its existing UCC financing statements filed
against any Borrowers owning such Bridge Loan Lien Property to reflect such
release as soon as practicable hereafter. In consideration of the foregoing,
Borrowers agree that the proceeds of the Bridge Loan shall be disbursed upon its
making as follows: (i) up to $390,000 shall be retained by the Bridge Loan
Lender, in payment of certain fees and charges owing to it or one or more of its
Affiliates by Borrowers; (ii) an additional $1,000,000 shall be retained by the
Bridge Loan Lender, thereafter to be held in escrow in anticipation of its use
in the payment of certain Indebtedness secured by all or portions of the Bridge
Loan Lien Property; and (iii) the rest and remainder thereof, aggregating at
least $5,110,000, shall be paid over to Lender for use, in part, to prepay in
full on the date hereof, the Term Loan, together with all accrued, but unpaid,
interest thereon, with the remainder thereof to be used to repay the Advances
(subject to their re-borrowing in accordance with the terms of the Credit
Agreement).

      3. Conditions to Effectiveness. The amendments set forth hereinabove are
further made contingent upon, and shall not become effective, unless and until:
(i) Borrowers shall have executed and delivered to WBCC this Amendment binding
themselves to all agreements (including amendments) set forth herein; (ii)
Lender shall have received, reviewed and approved the Bridge Loan Agreement, and
received a true, correct and complete copy thereof, as executed by and between
the parties thereto; (iii) the Bridge Loan shall have been made in substantial
accordance with the terms of the Bridge Loan Agreement; and (iv) the proceeds of
the Bridge Loan shall have been disbursed in conformity with Section 2.2 above
and the pay-off letter which is attached hereto as Exhibit "A" and by reference
made part, which shall be executed and delivered by Lender to Borrower on or
prior to the date of this Amendment.

      4. Effective Date. The amendments and modifications to the Credit
Agreement set forth in this Amendment shall be effective as of the date hereof
(except as otherwise expressly provided hereinabove).

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      5. No Other Changes. Except as expressly amended and modified hereby, the
terms of the Credit Agreement shall remain unchanged and continue in full force
and effect.

      6. Other Document. This Amendment constitutes an Other Document and shall
be governed and construed accordingly.

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Each of the parties has signed this Amendment as of the day and year first above
written.

                                      "BORROWERS"

                                      OMNI ENERGY SERVICES CORP.

                                      BY: /s/ G. Darcy Klug
                                          --------------------------------------
                                          G. Darcy Klug
                                          Executive Vice President

                                      AMERICAN HELICOPTERS INC.

                                      By: /s/ G. Darcy Klug
                                          --------------------------------------
                                          G. Darcy Klug
                                          Executive Vice President

                                      OMNI ENERGY SERVICES CORP.-MEXICO

                                      By: /s/ G. Darcy Klug
                                          --------------------------------------
                                          G. Darcy Klug
                                          Executive Vice President

                                      TRUSSCO, INC.

                                      By: /s/ G. Darcy Klug
                                          --------------------------------------
                                          G. Darcy Klug
                                          Executive Vice President

                                      TRUSSCO PROPERTIES, LLC

                                      By: /s/ G. Darcy Klug
                                          --------------------------------------
                                          G. Darcy Klug
                                          Executive Vice President

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                                      "LENDER"

                                      WEBSTER BUSINESS CREDIT
                                      CORPORATION

                                      By: /s/ [ILLEGIBLE]
                                          --------------------------------------
                                          Authorized Officer

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