Let me guess, you think water means amniotic fluid, even though NO PLACE in the entire bible is natural birth mentioned as "born of water"?
Natural birth is described as being "born of woman" never as "born of water". Gal. 4:4, Job 14:1 and Matthew 11:11 etc. are examples of how the bible refers to child birth. Did Jesus just decide to make up such a bizarre term for child birth on the fly?
"For as woman came from man, so also man is born of woman. But everything comes from God." 1st Cor. 11:12
If Jesus wanted to convey child birth to Nicodemus He could have simply said, "A man must be born of woman and of spirit".
If you want to believe that Jesus is meaning amniotic fluid, you go right ahead. I will just chalk it up as another stretch the trust only regeneration groups will go to in order to defend their theology.