There are literally hundreds of flood stories (myths) from many different cultures around the world. Here is a compilation. On hearing this, a typical fundamentalist response is 'See, Noach must be true! All these other stories confirm it'. However a global flood is pretty much impossible according to Science. Of course it could all have been a ness, except that the evidence shows it never happened. Of course maybe the ness also included cleaning up all the evidence afterwards too, but then that starts to get a little wierd. Hayim claims that maybe the flood water was magic water which left no mess. A mess-less ness! Could be, could be.
(Here are some difficulties with the concept of a global flood.)
Some people claim the flood was local to Mesopotamia, and when the Chumash repeatedly says 'all' (all the earth, all the heavens, all the animals etc) it just means 'all the local'. This is possible, but then what's the point of the story? A guy survives a small local flood on a boat with some animals. People on the edge of the flood were not affected, and while it might have been a big deal for that one guy, it certainly wasn't for the rest of the world. That doesn't really fit with the story, and you really have to stretch and kvetch a lot.
Another approach is Cassuto/Sarna, which I termed Myth Moshol. Flood mythology was very prevalent in the ancient near east, and the Israelites would certainly have been aware of it. However rather than accepting the Sumerian mythology of Utnapishtim, Gilgamesh or whatever, where the gods bring the flood because people were getting too noisy, the Torah turns the flood story into an ethical monotheistic morality story.
According to this, it turns out that Noach wasn't too real. This is upsetting to many people (me too), because we like Noach, even more than Adam. Also, it is jarring, since the Torah records some specific details about Noach's life and progeny, and accepting it as mythology makes the Torah look a little suspect.
Ultimately, there is no really satisfying answer to this problem (from an Orthodox perspective, if you are not Orthodox, it's not a question). I suppose I can sympathize with Rav Mattisyahu Solomon, who claimed we should all just say Taiku and wait for Moshiach. Meanwhile the flood story continues to inspire countless generations including mine, and at the last count we have the following:
- Flood themed crib set
- Noahs Ark painting
- Flood wallpaper border
- TevahTzedakah Box
- Tevah Menorah
- Fisher Price Noah's Ark Set
So what do I really think? I think there was cdertainly some major flood in Mesopotamia, probably about 8000 years ago. It's possible that there was a guy called Noach on a boat with a bunch of animals, who was saved miraculously. But somehow I doubt it. Still, believing in Noach is not one of the ikkarim, and saying that Noach was mythical is certainly NOT kefirah, contrary to the lunatic rantings of people like ZooShoteh (keshmo ken hu) and FKM (Freaking Kiruv Maniac).