They went into the ark by faith. Otherwise we have the admonition of Gal. Note that Nicodemus refers to entering back into his mother's womb and Jesus responds by saying that that which is of the flesh is flesh and spirit is spirit. Born of the water can mean natural birth. Read the context in John 3 .
Opinions are only opinions.
That settles it. The promise is the promise given to Abraham by God to justify people by faith. Again, calling upon His name is what forgives us of our sins. You tell me. Water doesn't wash our sins away.