I don't believe that either. (The evidence for earlier civilizations are underwater.)
I see goofy stuff in support of Atlantis or other prehistoric civilizations that might be underwater today, but nothing which even rises to the "hmmmm" level for me.
The lone exception to that is the theory about the Black Sea suddenly becoming inundated from the Mediterranean at some point, wiping out coastal communities and serving as the source of the legend of Gilgamesh and Noah's Flood. But the archeological evidence hasn't been found yet to truly support it.
That is interesting. Iraq seems to be one of the candidates for the earliest civilisation. This, coming so soon after the ice age would have to be in the tropical zone, so the options are a few -- the Mediterranean was a lake, and there are theories of there being really old Egyptian kings and really old Sumerian ones. The Indian cities off their western coast are also thousands of years old.