[RightWhale]

It's very unlikely that the seabed would drop 650 metres in 6,000 years

Sure it's not an everyday occurrence. A big earthquake could do the job, and there wouldn't be many records of the incident.

[blam]

"and there wouldn't be many records of the incident."

Just some rumors spread by Egyptian priests to some Greeks (Solon,Timeaus & Critias) and the rumors were recorded by a guy named Plato, eh?.