Aaaaaaaaaaaand that was the very point I was making. If they WERE identical they'd ALL say the same thing. They'd ALL say Noah, Mrs Noah, Ham, Sham, Curly and Wotsit.<quoted text>There are legends of this flood in all cultures of the world. Have you never heard of the Gilgamesh epic? These stories exist outside of the bible and are virtually identical. That is enough to prove Noahs' flood a reality.
You will note similarities lessen the further apart the sources are geographically. This is because local tribes plagiarized each other's myths, much like the Jews stole bits from the Egyptian pantheon, the Christians stole their myths from the Jews, and the Muslims stole theirs from the Jews and Christians.
That doesn't mean their religions are valid. It just means they weren't terribly inventive when they decided they wanted to make up a new religion.