You don't exactly do logic too well if you believe the flood story.
I saw someone say that before the flood, there was no rain, and water raised from the ground. That is painfully stupid.
Also, some will claim that the water evaporated. A second grade child could tell you that evaporated water will not leave earth's atmosphere, it will make the air humid and when there is enough, it will rain.
This means that all the water from the flood would still exist on earth. If we took all the water on earth, including evaporated water and ice, there would barely be enough to flood half of Europe.
It is utter nonsense, as is the rest of Genesis.