I love threads like this. We start with story about a man who survives a flood because he has a boat. It's the kind of thing that is happening everyday, somewhere on this planet. In this case, the story got embellished a little. Okay, maybe a lot. Whatever really happened, this particular flood certainly left an impression on everybody in the general vicinity. The story, as it has survived is incredible on the face of it. Even the limited zoology of the middle east would quickly swamp any boat that could be built with the available time and technology. Of course, building a boat with no propulsion or steering system simplifies things. All Noah had to do was build a "carpenter's boat," which is otherwise known as a waterproof box.
I think we can concede someone survived a flood in some kind of boat. Maybe he had his family with him. Maybe a few sheep and goats. Totally plausible, but once we establish the first impossibility, any additional impossibilities are superfluous.
Its more like ancient men noticed fossilized sea creatures on hills and mountains and some oriental tall tale tellers made up tall tales inspired by this fairly common observance. The tales were passed on and modified, changed and grew and grew. People like bizarre tales, witness all the myths of Greek monster killing heros and their monsters and the like.
It's best to go with the simplest explanation, in most cases. The ancient middle eastern cultures which left written records have flood stories of their own. Each story tells of someone who survived a cataclysmic flood by building a boat. The Genesis story of Noah is just one version.
It has been proposed that sea levels dropped greatly during the last ice age, leaving the large areas around the Black Sea dry. People lived, farmed, and raised animals by the sea shore. This scenario has an ice dam blocking the Straits of Bosporus. As levels in the Mediterranean Sea rose, this put greater pressure on the ice dam, until it collapsed and quickly brought the Black Sea back to its original level. In days or hours, the water level would rise a hundred feet or more. To anyone around at that time, it would appear to be the end of the world, something completely outside human experience. It's the sort of thing that would be talked about for a very long time.