It's in Christianity, in greek mythology, in some Asain religions, even in one Indian religion I remember there being just an ocean and the land was simply a giant turtle that rose up so people and creatures could live on it's back. I've heard it's in countless others. I've also heard they found a boat that could be described as an arc up in the mountains, although that was almost definitely a hoax. So here's what I'm wondering.

1. Is there any event, in history or geologically, that could have been perceived as a world-wide flood by the people living in the area?
2. Is there any evidence at all that the world was ever submerged? Or the majority of it?
3. If neither is the case, how could so many religions specifically share the tale of the world-wide flood?
4. Could it be that the story has been around for so long, it split off from an original tale into several different stories/religions as people separated?
5. If that were the case, it would have to be traced back countless centuries to an origin point before mankind was so spread out but while we were still able to communicate, what would a likely origin point be?

Thank you for your time!