Catholics and most Protestants disagree on the question of whether baptism saves us – Catholics viewing baptism as a requirement for salvation. One text Catholics cite is 1 Peter 3:20-21:
who formerly were disobedient, when once the Divine longsuffering waited in the days of Noah, while the ark was being prepared, in which a few, that is, eight souls, were saved through water.
There is also an antitype which now saves us––baptism (not the removal of the filth of the flesh, but the answer of a good conscience toward God), through the resurrection of Jesus Christ,
Before digging into the text a few preliminaries are in order. First, this passage is not part of an extended discourse on salvation, such as Paul undertakes in Romans and Galatians. Nor is Peter addressing the specific question of what must we do to be saved as Paul was in Acts 16:30-31. Rather, Peter is addressing the subject in passing as part of his larger discourse on suffering for Christ. Not to say that we cannot dig out little tidbits on salvation here; it’s just that we must be careful in doing so.
Second, Protestants believe that the scripture elsewhere teach justification by faith in such black and white terms that the sacramental view of salvation is ruled out. God promises to save believers and it would be wrong to think God would not save a true believer who was un-baptized. Now I do think contempt of baptism is a sign of unbelief. But if for some legitimate reason someone were to remain un-baptized (i.e. the thief on the cross) they will still be justified by their faith as God has promised.
On to the text... We have two reasons to believe Peter was speaking loosely when he says the waters of baptism save us: one in the inbound context and the other in the outbound context.
First, Peter says Noah and his family were saved by water. Strictly speaking, Noah was saved from water not by it. In light of this people have understood Peter’s statement in various ways. Some spiritualize the text by saying that the threat of water was the occasion on which Noah exercised faith and was justified. But this interpretation portrays Noah’s deliverance as spiritual rather than physical. The error in this view is plainly shown by the word ‘anittype’ - Noah’s physical deliverance from the flood typifies baptism rather than parallels it.
Others say Noah was saved ‘through’ water rather than by it. Thus Noah is being saved by something else while he passes through water. But that destroys the parallel with baptism as well, since with respect to baptism the passage says water saves us. Water is said to act in our salvation rather than simply to be around us as we are being saved.
Others say water buoyed up the ark or that water carried Noah to a new life. These views seem closer to being correct but these explanations are still not totally satisfying, since Noah would not have needed salvation in the first place if it were not for water and Noah’s life was not biologically different after the flood. In the final analysis, Peter is simply speaking loosely, water is a metonymy representing the whole business of God delivering Noah from the flood.
Second, Peter clarified what he was saying (i.e. not the removal of the filth of the flesh…). And this is a tell that Peter was speaking loosely and wanted to tighten up what he was saying a bit to avoid misunderstandings.
So what did Peter mean when he said water now saves us? I take water as a metonymy – both in the case of Noah’s salvation and ours. Strictly speaking water didn’t save Noah and it doesn’t save us, but it does represent our salvation and his. Baptism is a sign of the covenant. No one questions that; the question typically is if it’s more than that. In Genesis 17:13 God verbally substitutes His covenant for the sign of His covenant (i.e. I will put my covenant in your flesh). Here Peter substitutes the sign for the covenant.
One of the main reasons I take it that way is the expression “not the removal of the filth of the flesh, but the answer [or pledge] of a good conscience toward God”. In baptism, we pledge ourselves to God and join the visible church. If a believer is baptized, they are expressing their faith and God is saving them. If an unbeliever is baptized, he is not saved by it.
Babies are an interesting case, but without getting into that issue it seems safe to say babies neither pledge themselves to God nor are they bothered by conscience, so to say this passage teaches infant baptismal regeneration is quite a stretch.