There was an book by Graham Hancock, who is known mostly for very fringe theories on aliens and history, called Underworld where he argued that flood myths, which appear all over the world, were caused by an actual great flood caused by the melting of the ice sheets over North America during the last ice age. The reason it happened instantaneously as a flood and not a gradual rise in sea levels is because, or so he argues, the ice sheet melted and pooled in the middle (as ice does) and eventually broke through the ice walls.

Then, he claims that the water didn't go anywhere and argues that we have little evidence of human civilization and agriculture before the end of the last ice age is because the cities of humanity now currently exist under the sea, in areas which were once coastline before the sea level rose. He also argues that the greatest trove of new information about humanity is underwater, which on a whole has had very little archaeological research done.