A new twist on likes of the epic of Gilgamesh, as this is too recent for that. So it would have to be subsidence that sank it, but 15m is a LOT. Santorini?
Pozzuoli, Italy has had a ~3M uplift since 1982. It came in 2 stages, 1 during 1982-1984. Another during 2004-2005. Good thing it is not the other way around...
Seismically active region, to this day. Helike's newer and got splashed by a 373 BC tsunami combined with some subsidence that also accompanied the quake that brought the tsunami right up the Gulf of Corinth. A surviving ancient acc't describes submerged ruins up in the northern Aegean (mentioned in the book "Noah's Flood", where the authors claim it refers to a site on the Black Sea side, without any basis for the claim).