John 3:5 Reads "Jesus answered, “Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God.” (RSV). Could “born of water” be taken to mean childbirth?
First of all the liquid that surrounds the baby in the womb consists of more than just water. But even if it were just water, there would be no point to Jesus stating that unless one is born of water and the Spirit as He did. He would have no need to mention water at all. He would just say, “Unless one is born of the Spirit, he cannot enter the kingdom of God.” There had to be a reason for Jesus to mention water—plain and simple.
St. Paul speaks of baptism as the rite of initiation that replaces circumcision: “In him you have been circumcised with a circumcision not performed by human hand, but by the complete stripping of your body of flesh. This is circumcision according to Christ. You have been buried with him, when you were baptized; and by baptism, too, your have been raised up with him through your belief in the power of God who raised him from the dead.
Something really happens to the soul in baptism—as the Catholic Church has taught for two-thousand years.
Fr. Vincent Serpa, O.P.