-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 DJdpyn1Apa/ChkE2YPaN+TZogoSucHGuH/rw0ORFp4nXJhzuf4G66MoPiqI2rnHm
 v6RsZxovh0tRuPYDvNqTHQ==

<SEC-DOCUMENT>0001181431-03-013572.txt : 20030710
<SEC-HEADER>0001181431-03-013572.hdr.sgml : 20030710
<ACCEPTANCE-DATETIME>20030709185429
ACCESSION NUMBER:		0001181431-03-013572
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030709
FILED AS OF DATE:		20030710

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			SHORT JAY M PHD
		CENTRAL INDEX KEY:			0001205375

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-29173
		FILM NUMBER:		03780876

	BUSINESS ADDRESS:	
		STREET 1:		4955 DIRECTORS PLACE
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92121
		BUSINESS PHONE:		8585265151

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			DIVERSA CORP
		CENTRAL INDEX KEY:			0001049210
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMMERCIAL PHYSICAL & BIOLOGICAL RESEARCH [8731]
		IRS NUMBER:				223297375
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		4955 DIRECTORS PLACE
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92121
		BUSINESS PHONE:		858-526-5000

	MAIL ADDRESS:	
		STREET 1:		4955 DIRECTORS PLACE
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92121
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>rrd12961.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>4</documentType>
<periodOfReport>2003-07-09</periodOfReport>
<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0001049210</issuerCik>
        <issuerName>DIVERSA CORP</issuerName>
        <issuerTradingSymbol>DVSA</issuerTradingSymbol></issuer>
<reportingOwner>
<reportingOwnerId>
            <rptOwnerCik>0001205375</rptOwnerCik>
            <rptOwnerName>SHORT JAY M PHD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector>
<isOfficer>1</isOfficer>
<isTenPercentOwner>0</isTenPercentOwner>
<isOther>0</isOther>
<officerTitle>President, CEO &amp; CTO</officerTitle>
<otherText></otherText></reportingOwnerRelationship></reportingOwner>
<nonDerivativeSecurity>
<securityTitle>
<value>Common Stock</value></securityTitle>
<transactionDate>
<value>2003-06-26</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>M</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionTimeliness>
<value></value></transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>12794</value></transactionShares>
<transactionValue>
<value>0.5761</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>400657</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>I</value></directOrIndirectOwnership>
<natureOfOwnership>
<value>See Note</value>
<footnoteId id="F1"/></natureOfOwnership></ownershipNature></nonDerivativeSecurity>
<derivativeSecurity>
<securityTitle>
<value>Employee Stock Option (Right to Buy)</value></securityTitle>
<conversionOrExercisePrice>
<value>0.5761</value></conversionOrExercisePrice>
<transactionDate>
<value>2003-06-26</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>M</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionAmounts>
<transactionShares>
<value>12794</value></transactionShares>
<transactionValue>
<value>0.0000</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>D</value></transactionAcquiredDisposedCode></transactionAmounts>
<exerciseDate>
<value>1988-08-08</value>
<footnoteId id="F2"/></exerciseDate>
<expirationDate>
<value>2008-06-25</value></expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common Stock</value></underlyingSecurityTitle>
<underlyingSecurityShares>
<value>12794</value></underlyingSecurityShares></underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>847206</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></derivativeSecurity>
<footnotes>
<footnote id="F1">Includes 388,399 shares that are held by the RyCo 2001 Family Trust DTD 6/20/01; 1,786 shares that are held directly by the reporting person; 1,672 shares that are held of record by the reporting person&apos;s minor children; and, 8,800 shares that are held of record by the RyCo 2001 Irrevocable Trust DTD 6/62/01, the beneficiaries of which are the reporting person&apos;s minor children. The reporting person disclaims beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for purposes of Section 16 or for any other purpose.</footnote>
<footnote id="F2">On June 26, 2003, shares subject to the option totaling 860,000 were vested and exercisable.</footnote></footnotes>
<ownerSignature>
<signatureName>Martin A. Sabarsky, Atty-in-fact for Jay M. Short Ph.D.</signatureName>
<signatureDate>2003-06-27</signatureDate></ownerSignature></ownershipDocument>


</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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