<PAGE>
                                                                     EXHIBIT 4.4

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), OR ANY STATE SECURITIES LAW.
THESE SECURITIES MAY NOT BE SOLD OR OFFERED FOR SALE IN THE ABSENCE OF AN
EFFECTIVE REGISTRATION STATEMENT UNDER THE ACT AND ANY APPLICABLE STATE
SECURITIES LAWS, OR AN EXEMPTION THEREFROM.


                           DICKIE WALKER MARINE, INC.
                    SUBORDINATED CONVERTIBLE PROMISSORY NOTE

$___________                                             Promissory Note No. ___
                                                                  April 11, 2001


         FOR VALUE RECEIVED, the undersigned, Dickie Walker Marine, Inc., a
California corporation (the "Company"), does hereby promise to pay to the order
of ____________________ ("Holder"), at the Holder's address specified in the
signature page attached hereto, or at such other place as Holder may hereafter
designate in writing, the principal sum of $11,250.00 (the "Principal") and
interest thereon at the rate of seven percent (7%) per annum from the date
hereof until the first to occur of (i) the date on which the Principal and
accrued interest on this Promissory Note is converted into shares of the
Company's no par value common stock ("Common Stock") as provided in Section 1
below (the "Conversion Date"), (ii) the date on which Principal and accrued
interest is redeemed by the Company (the "Redemption Date"), or (iii) four years
from the date hereof (the "Maturity Date") at which time the Principal and all
accrued interest thereon shall be due and payable. Accrued interest shall be due
and payable semi-annually beginning on August 1, 2001, until the Conversion Date
or the Maturity Date, whichever occurs first, at which time all accrued but
unpaid interest shall be due and payable.

         1. CONVERSION.

              1.1 Conversion by Holder.

                  a. All or any portion of the Principal and accrued and unpaid
interest thereon may be converted (a "Conversion") at any time, at the election
of the Holder, into the number of shares of Common Stock equal to the Principal,
plus any interest then accrued, divided by $1.80 per share (the "Conversion
Price").

                  b. To effect a Conversion of this Promissory Note into shares
of Common Stock, the Holder shall deliver the original Conversion Notice in the
form attached hereto as Exhibit A ("Conversion Notice"), and this original
Promissory Note to the Company at its principal office to the attention of the
President. At its expense, the Company shall within thirty (30) days of its
receipt of the original Conversion Notice and this Promissory Note, issue and
deliver to Holder a certificate ("Certificate") evidencing the issuance of such
Common



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Stock to which the Holder is entitled upon such Conversion, together with any
cash amounts payable in lieu of the issuance of a fraction of a share of Common
Stock as described in Section 1.2 of this Promissory Note.

                  c. Conversion shall be deemed to be effective on the date of
such initial delivery of the Conversion Notice and this Promissory Note.
Thereafter, the Holder shall be treated for all purposes as the record holder of
such securities as of the date of conversion.

              1.2 Fractional Shares. No fractional shares of Common Stock will
be issued in connection with any Conversion hereunder, but in lieu of such
fractional shares the Company shall make a cash payment therefore in an amount
determined in such reasonable manner as may be prescribed by the Board of
Directors of the Company.

         2. REDEMPTION BY COMPANY.

              2.1 This Promissory Note may be redeemed by the Company in cash at
any time, at the option of the Company, at the following redemption prices, if
redeemed during the 12-month period beginning January 1 of the year indicated:

<Table>
<Caption>
                                                        Redemption Price
                                       Year                 Per Share
                                       ----             ----------------
<S>                                                     <C>
                                       2001                   $2.16
                                       2002                   $2.07
                                       2003                   $1.98
                                       2004                   $1.80
</Table>

              2.2 A notice of redemption ("Redemption Notice") shall be sent by
or on behalf of the Company, by first class mail, postage prepaid, to the Holder
of record at his/her/its respective addresses as it shall appear on the records
of the Company, not less than thirty (30) days nor more than sixty (60) days
prior to the Redemption Date (notifying such Holder of the election of the
Company to redeem the Promissory Note and of the date of the redemption), (ii)
stating the date on which the Promissory Note shall cease to be convertible, and
the Conversion Price, (iii) stating the place or places at which the Promissory
Note called for redemption shall, upon presentation and surrender of the
Promissory Note be redeemed, and the Redemption Price therefore, and (iv)
stating the name and address of the Redemption Agent, and the name and address
of the Company's transfer agent for the Promissory Note. The Company may act as
its own Redemption Agent and transfer agent for the Promissory Note.

              2.3 If a Redemption Notice shall have been given as hereinbefore
provided, and the Company shall not default in the payment of the Redemption
Price, then the Holder shall be entitled to all accrued interest until and
including the Redemption Date. From and after the Redemption Date the Note shall
no longer be deemed to be outstanding, and all rights of the



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Holders shall cease and terminate, except the right of the Holder, upon
surrender of Note, to receive amounts to be paid hereunder.

              2.4 The Company reserves the right to select which, if any,
outstanding Notes to redeem, and shall not be obligated to redeem this Note.

         3. SUBORDINATION. As used herein, "Senior Debt" is any secured
indebtedness of the Company, whether presently owed or incurred at any time in
the future, in favor of one or more banks, savings and loan associations,
institutions or other asset-based lenders in an aggregate amount, up to
$25,000,000. Upon receipt by the Company of notice from a lender of Senior Debt
that the Company is in default under any Senior Debt and continuing during the
period of such default (unless such lender has waived the default or has agreed
not to enforce any remedies with respect to such default), the indebtedness
evidenced by this Promissory Note shall be subordinated and subject in right of
payment to the prior payment in full of the Senior Debt and no payment of
Principal or interest on this Promissory Note shall be made by the Company.
Failure to make such payment while any Senior Debt is in default shall not be
deemed an Event of Default under this Promissory Note until the next due date
for accrued interest payments, or the Maturity Date, whichever occurs first;
provided, however, that notwithstanding the occurrence of any such Event of
Default on the next due date for accrued interest payments or the Maturity Date,
as applicable, payment of Principal and/or accrued interest hereon shall not be
paid so long as any Senior Debt remains in default and this Promissory Note
shall remain subordinated and subject in right of payment to all Senior Debt. If
this Promissory Note remains unpaid after the Maturity Date because it has been
subordinated as provided herein, Holder shall continue to have the right to
convert pursuant to Section 1 hereof until this Promissory Note is paid in full.
The Holder of this Promissory Note, by the purchase and acceptance hereof, does
hereby agree to and shall be bound by all the provisions contained herein
relating to such subordination.

         4. EVENTS OF DEFAULT. Subject to the limitation on defaults while
Senior Debt is in arrears as described in Section 3 of this Promissory Note, if
any of the following events shall occur (referred to herein as an "Event of
Default") and shall be continuing:

                  a. Default in the payment of accrued interest on the
semi-annual payment dates, or in the payment of Principal or accrued interest of
the Promissory Note on the Maturity Date; or

                  b. Default in the due observance or performance of any other
covenant, condition or agreement on the part of the Company to be observed or
performed pursuant to the terms hereof and such default continues for 20 days
after written notice thereof (specifying such default and making the request
that the same be remedied in accordance with this Section 4), has been received
by the Company and was sent by the Holder or Holders of at least 33-1/3% of the
principal amount of the Promissory Notes then outstanding (the Company to give
forthwith to all other holders of Promissory Notes at the time outstanding
written notice of the receipt of such notice specifying the default referred to
therein); or



<PAGE>

                  c. The entry of a decree or order by a court having
jurisdiction in the premises adjudging the Company as bankrupt or insolvent, or
approving as properly filed a petition seeking reorganization, arrangement,
adjustment or composition of or in respect of the Company under federal
bankruptcy laws or any other applicable federal estate law, or appointing a
receiver, liquidator, assignee, trustee, sequestrator (or other similar
official) of the Company or of any substantial part of its property or ordering
the winding up or liquidation of its affairs, and the continuance of any such
decree or order unstayed and in effect for a period of 60 consecutive days; or

                  d. The institution by the Company of proceedings to be
adjudicated as bankrupt or insolvent, or the consent by it to the institution of
bankruptcy or insolvency proceedings against it or the filing by it of a
petition or answer or consent seeking reorganization or release under federal
bankruptcy laws or any other applicable federal or state law, or the consent by
it to the filing of any such petition or to the appointment of a receiver,
liquidator, assignee, trustee, sequestrator (or other similar official) of the
Company or of any substantial part of its property, or the making by it of an
assignment for the benefit of creditors, or the admission by it in writing of
its inability to pay its debts generally as they become due or the taking of
corporate action by the Company in furtherance of any such action;

then, the Holder may, at its or their option, by notice to the Company, declare
the Promissory Note to be, and the Promissory Note shall upon the Company's
receipt of such notice be and become, forthwith due and payable together with
interest accrued thereon without presentment, demand, protest or further notice
of any kind, all of which are expressly waived by the Company to the extent
permitted by law.

         5. STOCK FULLY PAID; RESERVATION OF SHARES. All shares of Common Stock
which may be issued upon the exercise of the rights represented by this
Promissory Note will, upon issuance, be fully paid and nonassessable, and free
from all taxes, liens and charges with respect to the issue thereof. During the
period within which the rights represented by this Promissory Note may be
exercised, the Company will at all times have authorized, and reserved for the
purpose of the issue upon exercise of the conversion rights evidenced by this
Promissory Note, a sufficient number of shares of its Common Stock to provide
for the exercise of the rights represented by this Promissory Note.

         6. ADJUSTMENT OF CONVERSION PRICE. The number and kind of securities
issuable upon conversion of this Promissory Note and the Conversion Price shall
be subject to adjustment from time to time upon the occurrence of certain
events, as follows:

              6.1 Reclassification or Merger. In case of any reclassification or
change of outstanding securities or the shares of the Company's Common Stock
issuable upon conversion of this Promissory Note (other than a change in par
value, or from par value to no par value, or from no par value to par value) or
in case of any merger of the Company with or into another corporation (other
than a merger with another corporation in which the Company is a continuing
corporation and which does not result in any reclassification or change of



<PAGE>

outstanding securities issuable upon conversion of this Promissory Note), or in
case of any sale of all or substantially all of the assets of the Company, the
Company shall, as a condition precedent to such transaction, execute a new
Promissory Note or cause such successor or purchasing corporation, as the case
may be, to execute a new Promissory Note, providing that the holder of this
Promissory Note shall have the right to convert such new Promissory Note and
upon such conversion to receive, in lieu of each share of Common Stock
theretofore issuable upon exercise of this Promissory Note, the kind and amount
of shares of stock, other securities, money and property receivable upon such
reclassification, change or merger by the holder of one share of Common Stock.
Such new Promissory Note shall provide for adjustments which shall be as nearly
equivalent as may be practicable to the adjustments provided for in this Section
6. The provisions of this Section 6 shall similarly apply to successive
reclassifications, changes, mergers and sales of assets.

              6.2 Subdivision or Combination of Shares. If the Company at any
time while this Promissory Note remains outstanding, shall subdivide or combine
its Common Stock, the Conversion Price and the Redemption Price shall be
proportionately decreased in the case of a subdivision or increased in the case
of a combination.

              6.3 Stock Dividends. If the Company at any time while this
Promissory Note is outstanding shall pay a dividend with respect to Common Stock
payable in Common Stock, or make any other distribution with respect to Common
Stock (except any distribution specifically provided for in the foregoing
Sections 6.1 and 6.2) then the Conversion Price shall be adjusted, from and
after the date of determination of shareholders entitled to receive such
dividend or distribution, to that price determined by multiplying the Conversion
Price by a fraction (a) the numerator of which shall be the total number of
shares of Common Stock outstanding immediately prior to such dividend or
distribution, and (b) the denominator of which shall be the total number of
shares of Common Stock outstanding immediately after such dividend or
distribution.

         7. NOTICE OF ADJUSTMENT. Whenever the Conversion Price shall be
adjusted pursuant to Section 6 hereof, the Company shall make a certificate
signed by its chief financial officer setting forth, in reasonable detail, the
event requiring the adjustment, the amount of the adjustment, the method by
which such adjustment was calculated, and the Conversion Price and the
Redemption Price after giving effect to such adjustment, and shall cause copies
of such certificate to be mailed by first class mail, postage prepaid, to the
Holder.

         8. NOTICE OF CERTAIN ACTIONS. In the event that the Company shall
propose at any time:

                  a. to declare any dividend or distribution upon any class or
series of its stock, whether in cash, property, stock or other securities,
whether or not a regular cash dividend and whether or not out of earnings or
earned surplus;

                  b. to offer for subscription pro rata to the holders of any
class or series of its stock any additional shares of stock of any class or
series or other rights;



<PAGE>

                  c. to effect any reclassification or recapitalization of its
Common Stock outstanding involving a change in the Common Stock; or

                  d. to merge or consolidate with or into any other corporation,
or sell, lease or convey all or substantially all its assets or property, or to
liquidate, dissolve or wind up, whether voluntary or involuntary;

then in connection with each such event, this Company shall send to the Holder:

                  e. at least 10 days prior written notice of the date on which
a record shall be taken for such dividend, distribution or subscription rights
(and specifying the date on which the holders of Common Stock shall be entitled
thereto) or for determining rights to vote in respect of the matters referred to
in paragraphs a. and b. above;

                  f. in the case of the matters referred to in paragraphs c. and
d. above, at least ten (10) days prior written notice of the date for the
determination of shareholders entitled to vote thereon (and specifying the date
on which the holders of Common Stock shares shall be entitled to exchange their
Common Stock for securities or other property deliverable upon the occurrence of
such event); and

                  g. prompt notice of any material change in the terms of the
transaction described in a. through d. above.

         9. COMPLIANCE WITH SECURITIES ACT; NON-TRANSFERABILITY OF PROMISSORY
NOTE; DISPOSITION OF SHARES OF COMMON STOCK.

              9.1 Compliance with Securities Act. By acceptance hereof, Holder
agrees that this Promissory Note and the shares of Common Stock to be issued
upon conversion hereof are being acquired for investment and that it/he/she will
not offer, sell or otherwise dispose of this Promissory Note or any shares of
Common Stock to be issued upon conversion hereof except under circumstances
which will not result in a violation of the Securities Act of 1933, as amended
(the "Act"). In the absence of registration of the shares of Common Stock
issuable upon conversion of this Promissory Note, Holder shall confirm in
writing, in the form attached hereto as Exhibit B, that the shares of Common
Stock are being acquired for investment and not with a view toward distribution
or resale. In addition, Holder shall provide such additional information
regarding Holder's financial and investment background as the Company may
reasonably request, to confirm that Holder qualifies as an "accredited investor"
under the Act. All shares of Common Stock issued upon exercise of this
Promissory Note (unless registered under the Act) shall be stamped or imprinted
with a legend in substantially the following form:

                  "THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES
                  ACT OF 1933 (THE "ACT"). NO SALE OR DISPOSITION MAY BE
                  EFFECTED WITHOUT THE PRIOR WRITTEN CONSENT OF THE COMPANY AND
                  WITHOUT REGISTRATION UNDER THE ACT AND APPLICABLE STATE
                  SECURITIES LAWS, IF ANY, OR PURSUANT TO EXEMPTIONS THEREFROM."



<PAGE>

         10. RIGHTS OF SHAREHOLDERS. Holder shall not be entitled to vote or
receive dividends or be deemed the record owner of Common Stock or any other
securities of the Company which may at any time be issuable on the exercise
hereof for any purpose, nor shall anything contained herein be construed to
confer upon the Holder, as such, any of the rights of a shareholder of the
Company or any right to vote for the election of directors or upon any matter
submitted to shareholders at any meeting thereof, or to give or withhold consent
to any corporate action (whether upon any recapitalization, issuance of stock,
reclassification of stock, change of par value or change of stock to no par
value, consolidation, merger, conveyance, or otherwise) or to receive notice of
meetings, or to receive dividends or subscription rights or otherwise until the
Promissory Note shall have been converted and the shares purchasable upon the
conversion hereof shall have become deliverable, as provided herein.

         11. MISCELLANEOUS. The headings in this Promissory Note are for
purposes of convenience and reference only, and shall not be deemed to
constitute a part hereof. Neither this Promissory Note nor any term hereof may
be changed, waived, discharged or terminated orally but only by an instrument in
writing signed by the Company and Holder. All notices, requests and other
communications to any party hereunder shall be in writing (including telecopy or
similar writing) and shall be given to such party at its address contained in
the Company's records or such other address as such party may hereafter specify
in writing to the President of the Company for that purpose, or, if to the
Company, to Dickie Walker Marine, Inc., 470 Nautilus, Suite 312, La Jolla, CA
92037, to the attention of the President. Each such notice, request or other
communication shall be effective (i) if given by telecopy, when such message is
transmitted to the telecopy number contained in the Company's records or such
other number as a party may specify in writing to the Company at such address,
or (ii) if given by any other means, the earlier of (x) when delivered by hand
to the address contained in the Company's record or such other address as a
party may specify in writing to the Company at such address, or (y) five
business days after the mailing of such notice by certified mail.



<PAGE>

         IN WITNESS WHEREOF, the Company has caused this Promissory Note to be
executed in its name by the signature or facsimile signature of its President,
or by one of its Vice Presidents, and has caused its corporate seal to be hereto
affixed and attested by the signature or facsimile signature of its Chief
Financial Officer.


                                       DICKIE WALKER MARINE, INC.



                                       By:
                                          --------------------------------------
                                          Julia Sargent, President


ATTEST:


------------------------------------------
Gerald W. Montiel, Chief Financial Officer



<PAGE>

                                    EXHIBIT A

                              NOTICE OF CONVERSION


TO: DICKIE WALKER MARINE, INC.


         1. The undersigned hereby elects to convert $_______________, plus
accrued interest thereon, of this Promissory Note into the number of Shares of
Common Stock of Dickie Walker Marine, Inc. into which the Promissory Note
tendered herewith is convertible pursuant to its terms.

         2. Please issue a certificate or certificates in the name of the
undersigned or in such other names as is specified below


                     ---------------------------------------
                                     (Name)

                     ---------------------------------------

                     ---------------------------------------
                                    (Address)

         3. The undersigned represents that the aforesaid shares of Common Stock
are being acquired for the account of the undersigned for investment and not
with a view to, or for resale in connection with, the distribution thereof and
that the undersigned has no present intention of distributing or reselling such
shares. In support thereof, the undersigned has executed an Investment
Representation Statement attached hereto as Exhibit B.



                                       -----------------------------------------
                                                      (Signature)

------------------------
         (Date)