There are a few Scriptures which give the impression that water baptism is essential for salvation. But the overall teaching of Scripture is that sinners are justified (saved) by grace through faith in the Person and finished work of Christ (Acts 16:30,31; Rom 10:8-11; Eph 2:8,9). Because the true Bible teaching on water baptism makes salvation and baptism almost simultaneous, we have verses such as Mk 16:16, Acts 2:38, and 1 Pet 3:21.
So let's see exactly what Peter is telling us (KJV): 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:
Since Peter is comparing the deliverance of Noah and his family to water baptism, how exactly are they related?
1. Why was Noah saved from destruction? Because he found grace in the eyes of God (Gen 3:8).
2. Did the water save Noah or did the Ark? The Ark
3. Is the Ark a type of Christ? Yes
4. Is the Deluge a type of water baptism? Yes
5. Then what is Peter talking about? Water baptism is "the answer of a good conscience toward God". What exactly does that mean?
(a) The sinner repents and believes on the Lord Jesus Christ
(b) The moment he turns to Christ his sins are forgiven and he is justified (declared righteous) by God's grace
(c) Now the sinner's conscience is free from guilt for past sins
(d) Because the sinner died with Christ and rose again with Him ("by the resurrection of Jesus Christ"), water baptism symbolically confirms that his sins have been forgiven and his guilt has been removed
(e) Because baptism is the first step of Christian obedience, the saint maintains his good conscience by obeying Christ immediately, and being baptised as a believer.
How does this relate to Noah? Noah was in Christ (the Ark), then submerged in water (the Deluge), and then delivered from judgment (Hell) after the water receded. Was Noah already saved by grace? Absolutely. Was he subsequently saved from the Deluge? Absolutely. So did the water save Him, or was it God's grace? Purely God's grace.