It is just so difficult to understand how anyone of you think that the New Testament speaks what is not in the Old Testament, as you know that the only scripture those whom you read about in the New Testament had were the Old Testament writings.
They did not ever say, Water baptism doth now save us, at all, and you cannot find any such verse in the NT.
Their words and the idea of "dipping", which is their total thought in using the word baptism, was born here, and you have no excuse to not know it:
Exodus 12:22 "And ye shall take a bunch of hyssop, and dip it in the blood that is in the bason, and strike the lintel and the two side posts with the blood that is in the bason; and none of you shall go out at the door of his house until the morning."
The thought of that dipping or baptism at 1 Peter 3:21 is the dipping in the blood of Jesus.
Now enough of your nonsense about them reverencing plain water.
They did not go around inventing new beliefs. They obeyed what was written of the OT.