That is soul-shattering country, isn't it?
But the flood is not one of those things that has to be taken as a literal event. It could just be an intimation as to how God intends to make an end of all things earthly. He did promise to make an end of sin. The flood story could be mere warning.
Also, there is no proof that there is a God. I don't see how there ever could be. A relationship with God is based on faith. Not a scientific approach.