Science, physics, and mathematics as well as rational thinking has proven that Noah's Flood could never have happened at all. It could have been a local flood. I think it was not only a local flood but perhaps a blanding of legends of other post-Ice Age local floods. That is not the point in a religious discussion. The story, fictional as it was was incredibly IMMORAL.
1. Injustice: God murders all humans (men, women, children, babies, infants, and foetuses in pregnant women.) Why? Some adults had sinned in some way. That shows God to not be just but a cosmic killer alien of monstrous hate.
2. Injustice: God murders all non-human animals (a million million, non-human mammals, reptiles, birds, amphibians (all destroyed by salt water), fresh water fish, crustaceans, and smaller creatures.) This would have been an extinction event worse than the Permian Mass Extinction 251.4 million years ago in which 96% of all animal life died.
3. What sin could adult men possibly commit that warrented the deaths of millions or so women, children, babies, and foetuses plus a million million non-human animals?
What is so wrong with the story of Noah's Flood is not the fictional magic of how God murdered everyone but the immorality of the story. It is evil in its content and ideology.