This Rock has a pretty good summary of the case:
ONE key Scripture reference to being “born again” or “regenerated” is John 3:5, where Jesus states: “Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God.” This verse is so important that those who say baptism is just a symbol must deny that Jesus refers to baptism. “Born again” Christians claim that the water is the preached word of God. If we look at what the early Christians said about this verse, they uniformly referred to it as baptism and said this was the way in which we are born again and receive new life, a fact which can be shown elsewhere in Scripture (Rom. 6:3-4, Col. 2:12-13, Titus 3:5). It is impossible to find a Church Father who referred to John 3:5 as anything other than baptism; they are unanimous.
This Rock goes on to point out that all of the early Church Fathers agreed that this saying of Jesus refers to Baptism from Justin Martyr to St. Augustine and onward:
http://www.catholic.com/thisrock/1994/9410frs.asp
We are all born of water. The mother’s placenta is water. First we are born naturally and then, hopefully, we are born of the Spirit when we receive Christ into our lives. IMHO, of course. Baptism is not a born again experience. We must first be saved and THEN baptized. It is necessary but not until we’ve been born of the Spirit.