Exhibit
10.5





JOINDER
AGREEMENT


(Guaranty)





February
13, 2009





Re:
            Guaranty
      dated as of November 11, 2008 (as amended, restated, or supplemented from
      time to time, the “Guaranty”)
      executed by ELECTROWAVE USA, INC., a Nevada corporation, FLOTATION
      TECHNOLOGIES, INC., a Maine corporation, MAKO TECHNOLOGIES, LLC, a Nevada
      limited liability company, and DEEP DOWN INC., a Delaware corporation
      (each an “Existing
      Guarantor” and, collectively, the “Existing
      Guarantors”), in favor of WHITNEY NATIONAL BANK, a national banking
      association (“Lender”).





RECITALS





A.           DEEP
DOWN, INC., a Nevada corporation (“Borrower”),
and Lender entered into that certain Credit Agreement dated as of November 11,
2008 (as amended by First Amendment to Credit Agreement dated December 18, 2008,
Second Amendment to Credit Agreement dated February 13, 2009, and as further
amended, restated, or supplemented, the “Credit
Agreement”).





B.           DEEP
DOWN INTERNATIONAL HOLDINGS, LLC, a Nevada limited liability company (“New
Guarantor”), was recently organized and is or will become a direct
wholly-owned subsidiary of Borrower.





C.           To
comply with the terms and provisions of the Credit Agreement, New Guarantor and
Existing Guarantors have agreed to execute this Joinder Agreement for the
benefit of Lender.





AGREEMENT





NOW THEREFORE, for good and valuable
consideration, the receipt and adequacy of which is hereby acknowledged, the
parties hereto agree as follows:





1.           New
Guarantor hereby (a) agrees to become a “Guarantor” under the Guaranty, and (b)
joins in, becomes a party to, and agrees to comply with and be bound by all of
the terms and conditions of the Guaranty to the same extent as if New Guarantor
were an original signatory thereto.  New Guarantor shall hereafter be
jointly and severally liable for the performance of any and all past, present
and future obligations of any Guarantor under the Guaranty, it being understood
and agreed that any and all references in the Guaranty to “Guarantor” or
“Guarantors” shall include New Guarantor.





2.           New
Guarantor acknowledges that (a) Lender has agreed to extend credit to Borrower
for the purposes set forth in the Credit Agreement, (b) it is receiving direct
and indirect benefits from each such extension of credit, (c) the obligations of
the “Guarantor” or “Guarantors” under the Guaranty are the joint and several
obligations of each Guarantor, (d) certain representations and warranties set
forth in the Credit Agreement are in respect of it, and New Guarantor hereby
confirms that each such representation and warranty is true and correct, and (e)
certain covenants set forth in the Credit Agreement are in respect of it or
shall be imposed upon it, and New Guarantor covenants and agrees to promptly and
properly perform, observe, and comply with each such covenant.




3.           Capitalized
terms used but not defined herein have the meanings given them in the Credit
Agreement












[Signature is on the following
page.]
















IN
WITNESS WHEREOF, each of the undersigned has executed this Joinder Agreement
under seal as of the date first written above.








NEW
      GUARANTOR:
              
              DEEP
      DOWN INTERNATIONAL HOLDINGS, LLC,
              a
      Nevada limited liability company
              
              
              By:/s/ Eugene L.
      Butler
              Eugene
      L. Butler
              Chief
      Financial Officer
              
              
              EXISTING
      GUARANTORS:
              
              ELECTROWAVE
      USA, INC.,
              a
      Nevada corporation
              
              FLOTATION
      TECHNOLOGIES, INC.,
              a
      Maine corporation
              
              MAKO
      TECHNOLOGIES, LLC,
              a
      Nevada limited liability company
              
              DEEP
      DOWN INC.,
              a
      Delaware corporation
              
              
              By: /s/ Eugene L.
      Butler
              Eugene
      L. Butler
              Chief
      Financial Officer of each of the foregoing
  companies















Signature
Page to Joinder Agreement
 (Guaranty)