Well, while I don't believe in the greatest and most successful fairy tale of all time, there's tons of cultures who have a legend about a great flood. There was definitely one in the US at the end of the last ice age.
Having said that, there's no way Noah was able to build a wooden ship large enough to accommodate 10 million animals, plus mankind, plus provisions for the animals and mankind. You wouldn't even be able to fit that on a modern oil tanker that's half a mile long...