Written 6/25/200; edited 1/11/2018.
Jesus and his disciples practiced baptism, and baptism appears to be what is described by ὕδατος in John 3:5. But John adds πνεύματος in 3:5 and the preposition ἐξ that evidently controls both substantives (ἐξ ὕδατος KAI πνεύματος) which are apparently linked with the "birthing" process--an indication that spiritual rebirth or being born "from above," while it does involve water baptism is possibly not exhausted by water baptism (John 3:5 may indeed be a candidate for hendiadys or at the very least, water and spirit are intimately connected although I do not think the KAI in 3:5 is necessarily epexegetical). Now I am not saying that this is what every advocate of the baptism approach to John 3:3-5 is positing: just wanted to show where I stand on this issue.
Another question I have concerns Titus 3:5. In times of Christian antiquity, this verse was often construed as a proof for the necessity and nature of baptism. But I've never quite been able to understand how Titus 3:5 has anything to do with water immersion. What indicators from the NT itself support this interpretation?