I have done a little research in this area. The Med has been completely dry at least 40 times. The last time it was completely dry was five million years ago. There are scouring marks on the sea floor at the Gilbraltar entrance where the water gushed in at one time. I've not seen any dating of this scouring but some evidence suggests more recent times.(10-20k years ago) The Med could have stabilized at a much lower level than today (blocked at Gilbraltar) without completely drying. Also, I have proposed that something similar could have happened to the Gulf Of Mexico. The Gulf of Mexico could have been blocked from the worlds oceans during the last ice age across Florida, Cuba and the Yucatan or some of the associated islands. Consequently the Gulf of Mexico water level could have stabilized at a lower level and these structures could have been built along this coast and when the 'barrier' was broken these cities would have been submerged a half mile under water. This scenerio eliminates the need to explain all the subsidence that would have had to occur to place them this far under water. I have a url for a good underwater topography map that could lend some support for this idea. I will look for it and post it next.
ftp://ftp.ngdc.noaa.gov/GLOBE_DEM/pictures/GLOBALeb3colshade.jpg
A side note: A big cave complex has been found in my area here in Illinois originally named Burrows cave, but Burrows says his cave isn't the same but is nearby. Ancient Indian (not American Indian, India Indian!) artifacts from 5000 BC, I believe, have been found in it. The newest edition of "Ancient American" magazine has some of the details. I grew up in the Embarras River valley which is the valley where the cave is. I don't know if it's the same part of the valley, the cave's exact location is still being kept secret for fear of looting.