Re: Atlantis. There's a theory going around currently that the Black Sea was once a large inland lake, smaller and lower than now, with no connection to the Mediterranean. It had several villages around its shores. Rising sea levels due to the melting of ice at the end of the last ice age eventually caused water to break through the Bosporus, quickly (in geological terms) raising the water level in the Black Sea basin, inundating the villages and forcing their abandonment.

Although there is pretty strong evidence for the geological story, whether this is what gave rise to stories of the Biblical flood, or the sinking of Atlantis, is still pretty much conjecture.

Click here for a review in the journal Achaeology of the book Noah's Flood: The New Scientific Discoveries About the Event that Changed History by William Ryan and Walter Pitman.