-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 Es/FpX0KjNgbBDywq99UpYk9L9IoKx/1Of8CJFtFdK4Xfmoz+/keUZoD+MaTtmma
 kbzQ9+knWhjqzfQ2EP0MAg==

<SEC-DOCUMENT>0000351817-04-000047.txt : 20040601
<SEC-HEADER>0000351817-04-000047.hdr.sgml : 20040601
<ACCEPTANCE-DATETIME>20040601133332
ACCESSION NUMBER:		0000351817-04-000047
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20040601
FILED AS OF DATE:		20040601

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			HECKAMAN ALTON D JR
		CENTRAL INDEX KEY:			0001201969

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-08754
		FILM NUMBER:		04840626

	BUSINESS ADDRESS:	
		STREET 1:		STE 400
		STREET 2:		16825 NORTHCHASE DR
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77060
		BUSINESS PHONE:		2818742728

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SWIFT ENERGY CO
		CENTRAL INDEX KEY:			0000351817
		STANDARD INDUSTRIAL CLASSIFICATION:	CRUDE PETROLEUM & NATURAL GAS [1311]
		IRS NUMBER:				742073055
		STATE OF INCORPORATION:			TX
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		16825 NORTHCHASE DR STE 400
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77060
		BUSINESS PHONE:		2818742700

	MAIL ADDRESS:	
		STREET 1:		16825 NORTHCHASE DRIVE
		STREET 2:		SUITE 400
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77060
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>c0001201969d20040601f4f.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-06-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000351817</issuerCik>
        <issuerName>SWIFT ENERGY CO</issuerName>
        <issuerTradingSymbol>SFY</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001201969</rptOwnerCik>
            <rptOwnerName>HECKAMAN ALTON D JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>16825 NORTHCHASE DRIVE, SUITE 400</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77060</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CFO/Sr Vice President</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-06-01</value>
            </transactionDate>
            <deemedExecutionDate>
                <value>2004-06-01</value>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2554</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>9.979</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>24691</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6109</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>401(k)</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1076</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>ESOP</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Shares acquired under the SFY employee stock purchase plan.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Alton D. Heckaman, Jr.</signatureName>
        <signatureDate>2004-06-01</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----