[EVO X]

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...

[SunkenCiv]

Good call, the subsidence may have happened due to multiple events during the past 3000 years.