Except one is born of water and of the spirit he cannot enter the kingdom of God, says Jesus to Nicodemus. And you say it's not essential to salvation? Says who? Not Jesus.
Being born of water means being born from the womb. Sprinkling water on someone is not being born. No where in the Bible does anyone say water baptism is essential.
Here He is clearly says being born of the water is being born of the flesh.
"Jesus answered, “Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God. That which is born of the flesh is flesh, and that which is born of the Spirit is spirit."
(Joh 3:5-6 ESV)
