**...a figure, not literal.**
“....the days of Noah,....eight souls were saved by water. The like figure whereunto even baptism doth also now save us (not the putting away of the filth of the flesh, but the answer of a good conscience toward God,) by the resurrection of Jesus Christ.” 1Peter 3:20,21
For without the resurrection, baptism would be only vanity.
“Else what shall they do which are baptized for the dead, if the dead rise not at all? why are they then baptized for the dead?” 1Cor. 15:29
The “dead” in that verse is Jesus Christ, the subject of the previous 28 verses, who, of course is not dead, praise God!
The account of Noah (and his family) is a “type” of salvation by grace. The account tells us about Noah’s faith in what God told him – even though he couldn’t see what was happening, he trusted God. Noah and his family passed through the waters. The flood waters in this type represents condemnation, not salvation (being sealed into the arc) and not the means to salvation (faith and trust in God’s Word).
For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God, being put to death in the flesh, but quickened by the Spirit: By which also he went and preached unto the spirits in prison; Which sometime were disobedient, when once the longsuffering of God waited in the days of Noah, while the ark was a preparing, wherein few, that is, eight souls were saved by water. The like figure whereunto even baptism doth also now save us (not the putting away of the filth of the flesh, but the answer of a good conscience toward God,) by the resurrection of Jesus Christ: Who is gone into heaven, and is on the right hand of God; angels and authorities and powers being made subject unto him. 1 Peter 3:18-22 (ESV)
It is not the act of baptism which saves (“the removal of dirt from the flesh”), but what baptism signifies—the appeal to God for a good conscience.