<PAGE>

                                                                  EXHIBIT 4.2

THE SECURITIES REPRESENTED BY THIS CERTIFICATE AND THE SHARES OF COMMON STOCK 
AND OTHER SECURITIES, IF ANY, ISSUABLE UPON EXERCISE HEREOF HAVE NOT BEEN 
REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR ANY STATE 
SECURITIES LAWS.  SUCH SECURITIES MAY NOT BE SOLD OR TRANSFERRED UNLESS 
REGISTERED UNDER SUCH ACT AND ALL APPLICABLE STATE SECURITIES LAWS OR UNLESS, 
IN THE OPINION OF COUNSEL SATISFACTORY TO THE COMPANY, AN EXEMPTION FROM SUCH 
REGISTRATIONS IS AVAILABLE AT THE TIME OF SUCH SALE OR TRANSFER.

                                  WARRANTS TO
                             PURCHASE COMMON STOCK
                                      OF
                                AQUASEARCH, INC.

                           WARRANT CERTIFICATE NO. [___]

                           VOID AFTER DECEMBER 31, 1999

    This certifies that, for value received, [___________________] ("Buyer") 
or registered assigns (the "Holder") is the owner of [______] warrants (the 
"Warrants") of Aquasearch, Inc., a Colorado corporation (the "Company").  
Each Warrant shall entitle the registered holder thereof to purchase one 
share of the Company's Common Stock, $0.0001 par value (the "Common Stock"), 
at an exercise price per share of Common Stock equal to $1.00 per share (the
"Exercise Price"), at any time during the period commencing on the date of this
Warrant and expiring at 5:00 p.m. Honolulu, Hawaii time, on December 31, 1999
(the "Exercise Period"), all upon the terms and subject to the conditions set
forth herein.  After expiration of the Exercise Period, the Holder shall have no
right to purchase any Common Stock hereunder.  In the event that the aforesaid
expiration date of the Warrants falls on a day that is not a business day, then
the Warrants shall expire at 5:00 p.m. Honolulu, Hawaii time on the next
succeeding business day.  For purposes hereof, the term "business day" shall
mean any day other than a Saturday, Sunday or a day on which banking
institutions in Honolulu, Hawaii are authorized or obligated by law to be
closed.

    The Warrants are being issued pursuant to a securities purchase agreement 
between the Company and Buyer relating to the sale by the Company and the 
purchase by Buyer of an aggregate of [_____] units (the "Units"), each 
consisting of one share of Common Stock (the "Unit Common Stock") and one 
Warrant to purchase one share of Common Stock (the "Warrant Common Stock").  
The Warrant is one of a series of Warrants issued to multiple purchasers 
under substantially identical securities purchase agreements with the Company 
(hereinafter, together with the securities purchase agreement entered into 
between the Company and Buyer, the "Purchase Agreements").

    The Holder, by its or his acceptance hereof, agrees with the Company that 
the Warrants have been issued and all rights hereunder shall be held subject 
to all of the conditions, limitations and provisions set forth herein.

<PAGE>

    1.   EXERCISE OF WARRANTS.  The rights represented by the Warrants may be 
exercised in whole on one occasion at any time within the Exercise Period (a 
"Warrant Exercise Date") by (i) the surrender of the Warrants (with the 
purchase form at the end hereof properly executed) at the principal executive 
office of the Company or at the office of Wilson, Sonsini, Goodrich & Rosati,
650 Page Mill Rd., Palo Alto, California 94304 (telephone (415) 493-9300; 
facsimile (415) 493-6811), attention Steven L. Berson (the "Warrant Agent")
(or such other office or agency of the Company as it may designate by notice in
writing to the Holder at the address of the Holder appearing on the books of the
Warrant Agent), along with a Notice of Exercise in the form of EXHIBIT II 
hereto; and (ii) payment to the Company of the Exercise Price for the number 
of shares of Common Stock specified in the above-mentioned purchase form, 
together with applicable stock transfer taxes, if any.  Payment of the Exercise 
Price shall be made in cash or by certified or bank check payable to the 
Company.  The Warrants shall be deemed to have been exercised, immediately 
prior to the close of business on the date the Warrants are surrendered and 
payment is made in accordance with the foregoing provisions of this Paragraph 
1, and the person or persons in whose name or names the certificates for the 
Warrant Common Stock shall be issuable upon such exercise shall become the 
Holder or Holders of record of such Warrant Common Stock at that time and 
date.  The certificate  evidencing the Warrant Common Stock so purchased 
shall be delivered to the Holder within a reasonable time, after the rights 
represented by the Warrants shall have been so exercised.

    2.   RESTRICTIONS ON TRANSFER.  The Holder, by its or his acceptance 
hereof, hereby represents and warrants to, and agrees with, the Company as 
follows:  (i) the Holder has been informed that neither the Warrants, nor the 
shares of Warrant Common Stock or other securities purchasable pursuant to 
the Warrants, have been registered for sale under any federal or state 
securities laws and that the Warrants are being offered and issued to the 
Holder and, upon the exercise of the Warrants by the Holder, the Warrant 
Common Stock purchasable pursuant to the Warrants will be sold to the Holder, 
pursuant to an exemption from registration under the Securities Act of 1933, 
as amended (the "Securities Act"); (ii) the Holder is acquiring the Warrants and
will acquire the Warrant Common Stock purchasable upon exercise of the Warrants
for the Holder's own account and not with a view to distribution thereof; (iii) 
neither the Warrants nor such Warrant Common Stock may be sold, transferred, 
assigned, hypothecated or otherwise disposed of, in whole or in part, unless 
registered under the Securities Act and applicable state securities laws or 
unless, in the opinion of counsel satisfactory to the Company, an exemption 
from such registrations is available; and (iv) prior to the exercise of the 
Warrants the Holder shall provide to the Company in writing such information 
as the Company may reasonably request to establish that the exercise of the 
Warrants by the Holder is exempt from registration under such securities laws.

    Subject to the preceding paragraph, any assignment of Warrants shall be 
effected by the Holder by (i) completing and executing the Assignment Form 
attached as EXHIBIT III hereto and (ii) surrendering the Warrants represented 
hereby with such duly completed and executed transfer form for cancellation, 
accompanied by funds sufficient to pay any transfer tax, at the office or 
agency of the Company referred to in Paragraph 1; whereupon the Company shall 
issue, in the name or names specified by the Holder a new Warrant or Warrants 
of like tenor and representing in the aggregate rights to purchase the same 
number of shares of Warrant Common Stock as are then purchasable hereunder.

    3.   PAYMENT OF TAXES.  The Company will pay any documentary stamp taxes 
attributable to the initial issuance of Common Stock issuable upon the 
exercise of Warrants; PROVIDED, HOWEVER, that the Company shall not be 
required to pay any tax which may be payable in respect of any transfer 
involved in the issuance or delivery of any certificates of shares of Warrant 
Common Stock in a name

<PAGE>

other than that of the registered Holder of Warrants in respect of which such 
shares are issued, and in such case the Company shall not be required to 
issue or deliver any certificate for shares of Warrant Common Stock or any 
Warrant until the person requesting the same has paid to the Company the 
amount of such tax or has established to the Company's satisfaction that such 
tax has been paid.

    4.   RESERVATION OF COMMON STOCK.  There have been reserved, and the 
Company shall at all times keep reserved, out of its authorized but unissued
shares of Common Stock, the full number of shares of Common Stock sufficient to
provide for the exercise of the rights of purchase represented by the Warrants,
and the transfer agent for the shares of Warrant Common Stock and every
subsequent transfer agent for any shares of Warrant Common Stock issuable upon
the exercise of any of the aforesaid rights of purchase are irrevocably 
authorized and directed at all times to reserve such number of authorized 
shares of Common Stock as shall be required for such purpose.  The Company 
agrees that all shares of Warrant Common Stock issued upon exercise of the 
Warrants shall be, at the time of delivery of the certificates for such 
shares against payment of the Exercise Price therefor, validly issued and 
outstanding, fully paid and nonassessable.

    5.   NO RIGHTS OF SHAREHOLDER.  Prior to the exercise of any Warrants 
represented hereby, the Holder, as such, shall not be entitled to any rights 
of a shareholder of the Company, including, without limitation, the right to 
vote or to receive dividends or other distributions, and shall not be 
entitled to receive any notice of any proceedings of the Company, except as 
otherwise provided herein.

    6.   ADJUSTMENTS TO EXERCISE PRICE AND NUMBER OF SHARES.  The number and 
kind of securities purchasable upon the exercise of this Warrant and the 
Exercise Price shall be subject to adjustment from time to time as set forth 
in EXHIBIT I hereto upon the occurrence of certain events described therein.
The provisions of  EXHIBIT I are incorporated by reference herein with the 
same effect as if set forth in full herein.

    7.   NOTICES OF RECORD DATE.  In the event of any taking by the Company 
of a record of its shareholders for the purpose of determining shareholders 
who are entitled to receive payment of any dividend or other distribution, 
any right to subscribe for, purchase or otherwise acquire any share of any 
class or any other securities or property, or to receive any other right, or 
for the purpose of determining shareholders who are entitled to vote in 
connection with any proposed merger or consolidation of the Company with or 
into any other corporation (excluding any proposed merger or consolidation in 
which the shareholders of the Company immediately before such merger or 
consolidation will own more than 50% of the outstanding voting stock of the 
surviving entity), or any proposed sale, lease or conveyance of all or 
substantially all of the assets of the Company (other than the contribution 
of certain assets of the Company to a possible joint venture to be formed 
between the Company and Cultor Ltd. ("Cultor") pursuant to the terms of that 
certain Distribution and Development Agreement dated as of May 14, 1996 
including the exhibits thereto (collectively, the "Cultor Transaction")), or any
proposed liquidation, dissolution or winding up of the Company, then, in
connection with each such event, the Company shall mail to the Holder of this
Warrant at least twenty days prior written notice of the date on which any such
record is to be taken for the purpose of such dividend, distribution, right(s)
or vote of the shareholders.  Each such written notice shall specify the amount
and character of any such dividend, distribution or right(s), and shall set
forth, in reasonable detail, the matter requiring any such vote of the 
shareholders.

    8.   FRACTIONAL SHARES.  The Warrants may only be exercised to purchase 
full shares of Warrant Common Stock and the Company shall not be required to 
issue fractions of shares of Warrant Common Stock on the exercise of 
Warrants. However, if a Holder of Warrants exercises all Warrants then owned 
of record by him and such exercise would result in the issuance of a 
fractional share, the

<PAGE>

Company will pay to such Holder, in lieu of the issuance of any fractional 
share otherwise issuable, an amount of cash based on the Market Price of the 
Common Stock on the last trading day prior to the exercise date.  "Market 
Price" means, on any date, the average of the last reported sale price, or, 
in case no such reporting takes place on such day, the average of the last 
reported sale prices for the last three trading days, in either case as 
officially reported by the principal securities exchange on which the Common 
Stock is then listed or admitted to trading or as reported in the Nasdaq 
Stock Market, or, if the Common Stock is not listed or admitted to trading on 
any national securities exchange or quoted on the Nasdaq Stock Market, the 
closing bid quotation as furnished by the National Association of Securities 
Dealers, Inc. through NASDAQ or a similar organization if NASDAQ is no longer 
reporting such information, or if the Common Stock is traded on the NASD 
Electronic Bulletin Board, the closing bid price as furnished by NASDAQ, or 
if the Common Stock is not quoted on NASDAQ or the NASD Electronic Bulletin 
Board, as determined in good faith by resolution of the Board of Directors of 
the Company, based on the best information available to it for the day 
immediately preceding such issuance or sale, the day of such issuance or sale 
and the day immediately after such issuance or sale.  If the Common Stock is 
listed or admitted to trading on a national securities exchange and also 
quoted on the Nasdaq Stock Market, the Market Price shall be determined as 
hereinabove provided by reference to the prices reported in the Nasdaq Stock 
Market; provided that if the Common Stock is listed or admitted to trading on 
the New York Stock Exchange, the Market Price shall be determined as 
hereinabove provided by reference to the prices reported by such exchange.

    9.   REGISTRATION RIGHTS.  The rights of the Holder of this Warrant and the
obligations of the Company with respect to registration under the Securities Act
and the applicable rules and regulations thereunder shall be as set forth in
that certain Registration Rights Agreement dated as of October 1, 1996 between
the Company and the Buyer (the "Registration Rights Agreement"), the provisions
of which are incorporated by reference herein with the same effect as if set
forth in full herein.  The Warrant Common Stock shall be deemed "Registrable
Securities" as those terms are defined in the Registration Rights Agreement and
the Holder of this Warrant shall be deemed a "Holder," subject to all of the
rights and obligations thereunder.

    10.  MERGERS.  The Company agrees to provide the Holder of this Warrant 
with at least 20 days' prior written notice of the terms and conditions of 
any proposed transaction, in which the Company would (i) sell, lease, 
exchange, convey or otherwise dispose of all or substantially all of its 
property or business (other than the Cultor Transaction), or (ii) merge into 
or consolidate with any other corporation (other than a wholly-owned 
subsidiary of the Company), or effect any transaction (including a merger or 
other reorganization) or series of related transactions, in which more than 
fifty percent (50%) of the voting power of the Company is disposed of.  The 
Company will cooperate with the Holder in arranging the sale of this Warrant 
in connection with any such transaction.

    11.  MODIFICATION; WAIVER AND SEVERABILITY.  This Warrant and any 
provision hereof may be changed, altered, modified, amended, supplemented, 
discharged or terminated only with the written consent of the holders of a 
majority of the Warrants then outstanding issued pursuant to the Purchase 
Agreements.  In the event that any one or more of the provisions contained 
herein, or the application thereof in any circumstance, is held invalid, 
illegal or unenforceable, the validity, legality and enforceability of any 
such provision in every other respect and of the remaining provisions 
contained herein shall not be affected or impaired thereby, and the parties 
agree to cooperate with each other to 

<PAGE>

insure that each receives the economic benefits intended by any such 
provision that is so held to be invalid, illegal or unenforceable.

    12.  NOTICES.  Any notice, request or other document required or 
permitted to be given or delivered to the Holder hereof or the Company shall 
be delivered or sent to each such Holder at its address as shown on the books 
of the Warrant Agent or to the Company at 73-4460 Queen Ka'ahumanu Highway, 
Suite 110, Kailua-Kona, Hawaii, 96740 (or at such other address as may be 
designated in writing from time to time) and shall be deemed received by the 
Holder or the Company upon the earlier of actual receipt or, if sent by 
certified mail (postage fully pre-paid), five days after deposit in the 
U.S. mail.

    13.  BINDING EFFECT ON SUCCESSORS.  This Warrant shall be binding upon 
any corporation succeeding the Company by merger, consolidation or 
acquisition of all or substantially all of the Company's assets.  All of the 
obligations of the Company relating to the Warrant Common Stock shall survive 
the exercise and termination of this Warrant.  All of the covenants and 
agreements of the Company shall inure to the benefit of the successors and 
assigns of the Holder hereof. The Company will, at the time of the exercise 
of this Warrant, in whole or in part, upon request of the Holder hereof but 
at the Company's expense, acknowledge in writing its continuing obligation to 
the Holder hereof in respect of any rights (including, without limitation, 
any right to registration of the Warrant Common Stock  in accordance with the 
Registration Rights Agreement) to which the Holder hereof shall continue to 
be entitled after such exercise in accordance with this Warrant; PROVIDED, 
HOWEVER, that the failure of the Holder hereof to make any such request shall 
not affect the continuing obligation of the Company to the Holder hereof in 
respect of such rights.

    14.  LOST WARRANTS OR STOCK CERTIFICATES.  The Company covenants to the 
Holder hereof that upon receipt of evidence reasonably satisfactory to the 
Company of the loss, theft, destruction, or mutilation of this Warrant or any 
stock certificate issued upon exercise thereof and, in the case of any such 
loss, theft or destruction, upon receipt of an indemnity reasonably 
satisfactory to the Company, or in the case of any such mutilation upon 
surrender and cancellation of such Warrant or stock certificate, the Company 
shall make and deliver a new Warrant or stock certificate, of like tenor, in 
lieu of the lost, stolen, destroyed or mutilated Warrant or stock certificate.

    15.  NO IMPAIRMENT.  The Company will not, by amendment of its charter or 
through any reorganization, recapitalization, transfer of assets, 
consolidation, merger, dissolution, issue or sale of securities or any other 
voluntary action, avoid or seek to avoid the observance or performance of any 
of the terms to be observed or performed hereunder by the Company, but will 
at all times in good faith assist in the carrying out of all the provisions 
of this Warrant and in the taking of all such action as may be necessary or 
appropriate in order to protect the rights of the Holder of this Warrant 
against impairment.

    16.  DESCRIPTIVE HEADINGS.  The descriptive headings of the several 
paragraphs of this Warrant are inserted for convenience only and do not 
constitute a part of this Warrant.

    17.  RECOVERY OF LITIGATION COSTS.  If any legal action or other 
proceeding is brought for the enforcement of this Warrant, or because of an 
alleged dispute, breach, default, or misrepresentation in connection with any 
of the provisions of this Warrant, the successful or prevailing party or 
parties shall be entitled to recover reasonable attorneys' fees and other 
costs incurred in that action or proceeding, in addition to any other relief 
to which it or they may be entitled.

<PAGE>

    18.  GOVERNING LAW.  The Warrants shall be governed by and in accordance 
with the laws of the State of Hawaii without regard to the conflicts of law 
principles thereof.

            IN WITNESS WHEREOF, the Company has caused this Warrant to be 
executed by its duly authorized officer to take effect as of 
[_________________________________________].

                                    AQUASEARCH, INC.


                                    By:
                                        ----------------------------
                                        Mark E. Huntley, Ph.D.
                                        President and Chief Executive Officer


<PAGE>

                                   EXHIBIT I

                             ADJUSTMENT PROVISIONS


    1.   CAPITALIZED TERMS.  Capitalized terms used in this Exhibit I that are
not otherwise defined herein shall have the respective meanings assigned to
them in the Warrant, dated as of [________________________________________] to
which this Exhibit I is attached, if therein defined.

    2.   RECLASSIFICATION OR MERGER.  In case of any reclassification, change 
or conversion of securities of the class issuable upon exercise of this 
Warrant (other than a change in par value, or from par value to no par value, 
or from no par value to par value, or as a result of a subdivision or 
combination), or in case of any merger of the Company with or into another 
corporation or entity (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 outstanding securities issuable upon exercise 
of this Warrant), or in case of any sale of all or substantially all of the 
assets of the Company, the Company, or such successor or purchasing 
corporation or entity, as the case may be, shall execute a new Warrant (in 
form and substance satisfactory to the Holder of this Warrant) providing that 
the Holder of this Warrant shall have the right to exercise such new Warrant 
and upon such exercise to receive, in lieu of each share of Warrant Common 
Stock theretofore issuable upon exercise of this Warrant, the kind and amount 
of shares of stock, other securities, money and property receivable upon such 
reclassification, change or merger by a holder of one share of Common Stock.  
Such new Warrant shall provide for adjustments that shall be as nearly 
equivalent as may be practicable to the adjustments provided for in this 
Exhibit I.  The provisions of this Section 2 shall similarly apply to successive
reclassifications, changes, mergers and transfers.

    3.   SUBDIVISION OR COMBINATION OF SHARES.  If the Company at any time
while this Warrant remains outstanding and unexpired shall subdivide or combine
its Common Stock, the Exercise Price and the number of Shares issuable upon
exercise hereof shall be proportionately adjusted.

    4.   STOCK DIVIDENDS.  If the Company at any time while this Warrant is 
outstanding and unexpired shall pay a dividend payable in shares of Common 
Stock, then the Exercise 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 Exercise Price in 
effect immediately prior to such date of determination 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 and the number of 
shares of Warrant Common Stock subject to this Warrant shall be 
proportionately adjusted.

    5.   OTHER DISTRIBUTIONS.  In the event the Company shall declare a 
dividend or distribution payable in cash, securities of other persons, 
evidences of indebtedness issued by the Company or other persons, assets or 
options or rights not referred to in Sections 2, 3 or 4 of this Exhibit I, then,
in each such case, provision shall be made by the Company such that the holder
of this Warrant shall receive upon exercise of this Warrant a proportionate
share of any such dividend or distribution as though it were the

<PAGE>

Holder of the shares of Warrant Common Stock as of the record date fixed for 
the determination of the shareholders of the Company entitled to receive such 
dividend or distribution.

    6.   NOTICE OF ADJUSTMENTS.  Whenever the Exercise Price shall be 
adjusted pursuant to the provisions hereof, the Company shall within thirty 
days of such adjustment deliver a certificate signed by its Chief Financial 
Officer to the registered Holder(s) hereof 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 Exercise Price after 
giving effect to such adjustment.


<PAGE>

                                   EXHIBIT II

                               NOTICE OF EXERCISE

To:  Aquasearch, Inc.
     73-4460 Queen Ka'ahumanu Highway
     Suite 110
     Kailua-Kona, Hawaii  96740

    1.   The undersigned hereby elects to purchase __________ shares of Common
Stock of the Company pursuant to the terms of the attached Warrant, and tenders
herewith payment of the purchase price of such shares in full; or

    2.   Please issue a certificate or certificates representing said shares in
the name of the undersigned or in such other name or names as are specified
below:


        Name:    ________________________________________


        Address: ________________________________________


                 ________________________________________


    3.   The undersigned represents that the aforesaid shares 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.



_______________
    (DATE)


                                           ____________________________________
                                                      (SIGNATURE)

<PAGE>

                                  EXHIBIT III

                                ASSIGNMENT FORM

                   (To assign the foregoing Warrant, execute
                 this form and supply the required information.
                    Do not use this form to purchase shares.)


    FOR VALUE RECEIVED, the undersigned hereby, sells, assigns and transfers
unto:

____________________________________________________________________

whose address is ___________________________________________________
                                 (Please Print)

and whose Social Security or other Taxpayer Identification 
Number is: ________________________________________________________,

the foregoing Warrant and all rights thereunder, hereby constituting and
appointing ______________________________________ to transfer said Warrant on
the books of the Company, with full power of substitution in the premises.

    Dated: ______________, 19__.

    Holder's Signature: ________________________

    Holder's Name: _____________________________
                           (Please Print)

    Holder's Address: __________________________
                           (Please Print)

    ____________________________________________


Signature Guaranteed: ____________________________________________


NOTE:  The signature to this Assignment Form must correspond with the name as 
it appears on the face of the Warrant, without alteration or enlargement or 
any change whatever, and must be guaranteed by a bank or trust company or by 
a member of the National Association of Securities Dealers, Inc.  Officers of 
corporations and those acting in a fiduciary or other representative capacity 
should file proper evidence of authority to assign the foregoing Warrant.