While rejecting baptismal regeneration, Craig Blomberg does note the problem with reading “water” in John 3:5 as being related to the natural birth (whether as a reference to semen or amniotic fluid):
Even less likely [than the baptismal regeneration reading] is the idea that “born of water” has something to do with the physiology of natural birth (as a euphemism for semen or a reference to the mother’s water breaking). Instead, the historical, literary, and grammatical data all converge to support the interpretation that Jesus is referring to the inward cleansing that God works through his Spirit in human hearts when they turn to him. That this may (and even should) be then symbolized by baptism is very appropriate, but that is not Jesus’s primary thrust. (Craig L. Blomberg, Jesus the Purifier: John’s Gospel and the Fourth Quest for the Historical Jesus [Grand Rapids, Mich.: Baker Academic, 2023], 246, comment in square brackets added for clarification)
