EXHIBIT 4.16

                                                                      Document 1

                                                           Contract No. MA-13509

                       COMMITMENT TO GUARANTEE OBLIGATION

                                       by

                          THE UNITED STATES OF AMERICA

                                   Accepted by

                             PETRODRILL FIVE LIMITED

                                    Shipowner

                   (Under Title XI, Merchant Marine Act, 1936,
                        as amended, and in effect on the
                       date of this Guarantee Commitment)
                   -------------------------------------------

                                TABLE OF CONTENTS

DOC
NO.   DOCUMENT
- - ---   --------------------------------------
 1.   Commitment to Guarantee Obligations
      Schedule One -- Form of Opinion of
 2    Counsel
      Appendix I -- Form of Credit
 3    Agreement
      Appendix II -- Form of Trust
 4    Indenture
      Schedule A -- Schedule of
 5    Definitions to the Trust Indenture
      Exhibit 1 -- General Provisions
      Incorporated into the Trust
 6    Indenture by Reference
      Exhibit 2 -- Form of Floating Rate
 7    Note
      Exhibit 3 -- Form of Fixed Rate
 8    Note
      Exhibit 4 -- Form of Authorization
 9    Agreement
      Exhibit 5 -- Form of Secretary's
10    Supplemental Indenture
      Appendix III -- Form of Security
11    Agreement
      Exhibit 1 -- General Provisions
      Incorporated into the Security
12    Agreement by Reference
      Schedule X -- Schedule of
13    Definitions
      Exhibit 2 -- Form of Secretary's
14    Note
      Exhibit 3 -- Form of First
15    Preferred Ship Mortgage
      Exhibit 4 -- Form of Title XI
      Reserve Fund and Financial
16    Agreement
      Exhibit 5 -- Form of Consent of
17    Shipyard
18    Exhibit 6 -- Construction Contract
      Exhibit 7 -- Form of Depository
19    Agreement

                       COMMITMENT TO GUARANTEE OBLIGATIONS

                                       BY

                          THE UNITED STATES OF AMERICA

                                   accepted by

                             PETRODRILL FIVE LIMITED

                                    Shipowner

     THIS COMMITMENT TO GUARANTEE OBLIGATIONS, dated as of April 9, 1999 (the
"Guarantee Commitment"), is made and entered into by the UNITED STATES OF
AMERICA (the "United States"), represented by the SECRETARY OF TRANSPORTATION,
acting by and through the MARITIME ADMINISTRATOR (the "Secretary"), and accepted
on said date by PETRODRILL FIVE LIMITED, a British Virgin Islands international
business company (the "Shipowner").

RECITALS

     A. The Shipowner will be the sole owner of the dynamic positioned
semi-submersible drilling vessel to be named AMETHYST 5 ("the Vessel"), built
pursuant to the Construction Contract with TDI-Halter, Limited Partnership (the
"Shipyard").

     B. To aid in financing the construction of the Vessel, the Shipowner will
borrow an aggregate principal amount equal to 87 1/2% of the Actual Cost of the
Vessel, as of the Closing Date. To accomplish such financing, the Shipowner has
accepted this Guarantee Commitment subject to the terms and conditions set forth
herein.

     C. The Shipowner has entered into the Credit Agreement providing for the
sale and delivery of obligations in the aggregate principal amount of
$150,183,000 to be designated "United States Government Guaranteed Export Ship
Financing Obligations, AMETHYST 5 Series" (the "Obligations") having the
maturity date and interest rate set forth in the Credit Agreement, the Indenture
and the Obligations.

     D. As security for the Guarantees and the Secretary's Note, the Shipowner
will execute and deliver the Security Agreement, Contract No. MA-13511, and the
following agreements shall be executed and delivered: the Indenture, the
Authorization Agreement, Contract No. MA-13510, the Secretary's Note, the
Mortgage, Contract No. MA-13512, the Financial Agreement, Contract MA-13513, and
the Depository Agreement, Contract No. MA-13514.

                              W I T N E S S E T H:

     That under the provisions of Title XI of the Merchant Marine Act, 1936, as
amended and in consideration of (i) the covenants of the Shipowner contained
herein and (ii) other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the Secretary hereby commits
itself as herein provided.

                                    ARTICLE I
                    FINDINGS AND DETERMINATIONS OF SECRETARY

     Pursuant to Section 1103(g)(i) of Title XI, the Secretary has determined
that the issuance of this Guarantee Commitment will not result in the denial of
an economically sound application to issue a commitment to guarantee obligations
for a Vessel documented under the laws of the United States.

     Pursuant to Section 1104A(b)(1) of Title XI, the Secretary has approved the
Shipowner as responsible and possessing the ability, experience, financial
resources and other qualifications necessary to the adequate operation and
maintenance of the Vessel.

     Pursuant to Section 1104A(b)(2) of Title XI, the Secretary has determined
that the aggregate of the Actual Cost of the Vessel is $171,638,175. Prior to
the Closing Date, the Secretary, in its discretion, may redetermine the actual
Cost of the Vessel.

     On the Closing Date, the aggregate principal amount of the Obligations will
not exceed 87 1/2% of the Actual Cost of the Vessel.

     Pursuant to Sections 1104A(b)(3), 1104A(b)(4) and 1104A(b)(5) of Title XI,
the Secretary has determined that: (1) the maturity date of the Obligations is
satisfactory, (2) payments of principal required by the Obligations are
satisfactory, and (3) the interest rate to be borne by the Obligations to be
issued on the Closing Date is reasonable.

     Pursuant to Section 1104A(d) of Title XI, the Secretary has found that the
Shipowner's proposed use of the Vessel will be economically sound.

     Pursuant to Section 1104A(d)(A) of Title XI, the Secretary has determined
that the construction, reconstruction or reconditioning of the Vessel will aid
in the transition of United States shipyards to commercial activities or will
preserve shipbuilding assets that would be essential in time of war or national
emergency.

     The Secretary has further determined that the Secretary of Defense has
received notice of the Secretary's receipt of application and that the Secretary
of Defense has not disapproved the loan guarantee pursuant to the authority,
under Section 1104A(j)(1) of Title XI, to assess whether the potential use of
the Vessel may cause harm to the United States national security interests.

     The Secretary has determined that the countries in which the Shipowner has
its chief executive offices or has located a substantial portion of its assets
present an acceptable financial and legal risk to the Secretary's Security.

                                   ARTICLE II
                       COMMITMENT TO GUARANTEE OBLIGATIONS

     The United States, represented by the Secretary, HEREBY COMMITS ITSELF TO
GUARANTEE the payment of the unpaid interest on, and the unpaid balance of the
principal of, the Obligations, including interest accruing between the date of
default under the Obligations and the payment in full of the Guarantees, and, to
effect this Guarantee Commitment, hereby commits itself to execute and deliver
the Authorization Agreement, Security Agreement, Financial Agreement, and
Depository Agreement on the Closing Date pursuant to the terms of the Guarantee
Commitment.

                                   ARTICLE III
                                 THE OBLIGATIONS

     The Obligations shall be as provided in the Indenture and in the form of
the Obligations annexed as Exhibits 2 and 3 to the Indenture. The Obligations
shall be subject to all of the terms and conditions set forth in the Indenture.

                                   ARTICLE IV
             CONDITIONS TO EXECUTION AND DELIVERY OF THE GUARANTEE

     The obligation of the Secretary to execute and deliver the Guarantee on the
Closing Date shall be subject to the following conditions unless waived in
writing by the Secretary:

     (a) the Closing Date shall occur on or prior to September 11, 1999.

     (b) the Shipowner and the Shipyard shall have executed and delivered to the
Secretary a copy of the Construction Contract, as amended, and the Shipyard
shall have executed the Consent of Shipyard.

     (c)  the Shipowner shall have executed and delivered the following
documents in the form attached hereto: the Security Agreement, Financial
Agreement, Trust Indenture, Secretary's Note, Obligations, Credit Agreement, and
Depository Agreement;

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     (d) the Indenture Trustee shall have executed, in the form attached hereto,
the Authorization Agreement and Trust Indenture; the Depository shall have
executed the Depository Agreement; and the Lender shall have executed the Credit
Agreement;

     (e) the following documents shall have been delivered to the Secretary: (i)
one executed counterpart and one copy of the Credit Agreement; (ii) two executed
counterparts of the Trust Indenture, (iii) two specimen copies of the
Obligations; (iv) two executed originals of the legal opinion issued under
section (j) of this Article; (v) two copies of the legal opinion delivered to
the Lender pursuant to the Credit Agreement, and (vi) two originals of all other
documents delivered by the Shipowner, Indenture Trustee or the Depository in
connection with this Closing.

     (f) the Shipowner shall have executed an Officer's Certificate representing
and warranting the truth of the following statements as of the Closing Date:

          (i)  each of the representations and warranties set out at Section
     2.01 of the Security Agreement; and

          (ii) the Shipowner is not in violation of any Federal laws having a
     substantial adverse effect on the interests of the United States of America
     and that the consummation of the Commitment would not violate non-Title XI
     Federal law.

     (g) the Secretary shall have received the Guarantee Fee payable under
Section 1104A(e) of Title XI and the Investigation Fee, due under Section
1104A(f) of Title XI.

     (h) the Shipowner shall have complied in all material respects with its
agreements under this Guarantee Commitment;

     (i) there shall not have occurred any event which constitutes (or after any
period of time or any notice, or both, would constitute) a "Default" under the
Security Agreement;

     (j) there shall have been delivered to the Secretary by the Shipowner
opinions of counsel admitted to the appropriate jurisdictions of the United
States and British Virgin Islands, the Commonwealth of the Bahamas, and the
Federative Republic of Brazil acceptable to the Secretary, in the form annexed
hereto as Schedule One which shall include, among other things, an opinion to
the effect that: (i) by the terms of the Security Agreement, the Shipowner has
granted to the Secretary a fully perfected, first priority security interest in
each of the assets which constitutes the Security; and (ii) all filings,
recordings, notice and other actions required to perfect the Secretary's
interest in the Security and to render such security interest valid and
enforceable under applicable law have been duly effected:

     (k) Petrodrill Four Limited shall have executed and delivered to the
Secretary its guarantee of the Title XI debt of the Shipowner.

     (l) Each of Pride International, Inc. and Maritima Petroleo E Engenharia
Ltda. shall have executed and delivered to the Secretary its guarantee of final
charges that may be assessed against the Vessel due to late arrival penalties
and/or ad valorem taxes in an amount not to exceed $20,500,000.

     (m) the Secretary shall have received a letter agreement from the Shipowner
to provide the Secretary within a reasonable time after the Closing Date, with
eight (8) conformed copies of the Guarantee Commitment and each of the
Appendices and Exhibits thereto executed on or prior to such date;

     (n) on the Closing Date, the qualifying requirements set forth in Section
10 of the Financial Agreement shall have been complied with and certified to as
required therein; and

     (o) at least fifteen (15) Business Days prior to the Closing Date, there
shall have been delivered to the Secretary, pro forma balance sheets for the
Shipowner as of the Closing Date, certified by an officer of the Shipowner
showing, among other things, all non-Title XI debt of the Shipowner;

     (p) on the Closing Date, the Shipowner shall certify that all non-Title XI
loans to the Shipowner relating to the Vessel has been discharged or
subordinated satisfactorily to the Secretary, and

     (q) at least ten (10) days prior to the Closing Date, the Shipowner shall
have provided the Secretary with satisfactory evidence of insurance as required
by the Security Agreement.

                                     - 3 -

     (r) on the Closing Date, the Secretary shall be a beneficiary under the
Shipyard's performance and labor and material payments bonds, which bonds shall
be in form and substance satisfactory to the Secretary.

     (s) on the Closing Date, the Shipowner and Amethyst Financial Company
Limited shall issue a declaration regarding lobbying activities pursuant to the
provisions of 31 U.S.C. 1352.

                                    ARTICLE V
                        VARIATION OF GUARANTEE COMMITMENT

     No variation from the terms and conditions hereof shall be permitted except
pursuant to an amendment executed by the Secretary and the Shipowner.

                                   ARTICLE VI
                TERMINATION OR ASSIGNMENT OF GUARANTEE COMMITMENT

     This Guarantee Commitment may be terminated and the parties hereto shall
have no further rights or obligations hereunder, upon written notice by the
Secretary of the termination of the obligations of the United States pursuant to
the Shipowner's failure to satisfy one or more conditions set forth in Article V
hereof or upon the Secretary's determination, at or before the Closing Date,
that (i) the Shipowner is in violation of Federal law and such violation would
have a substantial, adverse affect on the interests of the United States of
America or (ii) the consummation of the Commitment would violate non-Title XI
Federal law. The Shipowner's warranties and representations shall survive the
termination of this Agreement and the Secretary's issuance of the Guarantees.
This Guarantee Commitment may not be assigned by the Shipowner without the prior
written approval of the Secretary and any attempt to do so shall be null and
void AB INITIO.

                                   ARTICLE VII
                 GOVERNING LAW; JURISDICTION AND CONSENT TO SUIT

     This Guarantee Commitment hereby adopts and incorporates by reference as if
fully set forth herein the provisions relating to Jurisdiction and Consent to
Suit of the Special Provisions of the Security Agreement.

                                  ARTICLE VIII
                                  MISCELLANEOUS

     (a) The table of contents and the titles of the Articles are inserted as a
matter of convenient reference and shall not be construed as a part of this
Guarantee Commitment. This Guarantee Commitment may be executed in any number of
counterparts, each of which shall be an original, but such counterparts shall
together constitute but one and the same instrument.

     (b) For all purposes of this Guarantee Commitment, unless otherwise
expressly provided or unless the context shall otherwise require, capitalized
terms used herein shall have the meaning given in Schedule X to the Security
Agreement.

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     IN WITNESS WHEREOF, this Commitment to Guarantee Obligations has been
executed by the United States and accepted by the Shipowner, all as of the day
and year first above written.

                                          UNITED STATES OF AMERICA,
                                          SECRETARY OF TRANSPORTATION


(SEAL)                                 MARITIME ADMINISTRATION

Attest:                                BY:  /s/Joel C. Richard
                                       Secretary
                                       Maritime Administration
/s/Larry Main
Assistant Secretary

                                       ACCEPTED BY:
                                       PETRODRILL FIVE LIMITED
                                       as Shipowner

                                       BY:  /s/Earl W. McNiel
                                       Treasurer

Attest:

BY:  /s/ Robert W. Randall
      Secretary

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