Interesting. I've been looking for an underwater mud volcano because of this:
From Plato's Critias:
Let me begin by observing first of all, that nine thousand was the sum of years which had elapsed since the war which was said to have taken place between those who dwelt outside the Pillars of Heracles and all who dwelt within them; this war I am going to describe. Of the combatants on the one side, the city of Athens was reported to have been the leader and to have fought out the war; the combatants on the other side were commanded by the kings of Atlantis, which, as was saying, was an island greater in extent than Libya and Asia, and when afterwards sunk by an earthquake, became an impassable barrier of mud to voyagers sailing from hence to any part of the ocean.
From Plato's Timaeus:
Many great and wonderful deeds are recorded of your state in our histories. But one of them exceeds all the rest in greatness and valour. For these histories tell of a mighty power which unprovoked made an expedition against the whole of Europe and Asia, and to which your city put an end. This power came forth out of the Atlantic Ocean, for in those days the Atlantic was navigable; and there was an island situated in front of the straits which are by you called the Pillars of Heracles; the island was larger than Libya and Asia put together, and was the way to other islands, and from these you might pass to the whole of the opposite continent which surrounded the true ocean; for this sea which is within the Straits of Heracles is only a harbour, having a narrow entrance, but that other is a real sea, and the surrounding land may be most truly called a boundless continent.
Now in this island of Atlantis there was a great and wonderful empire which had rule over the whole island and several others, and over parts of the continent, and, furthermore, the men of Atlantis had subjected the parts of Libya within the columns of Heracles as far as Egypt, and of Europe as far as Tyrrhenia. This vast power, gathered into one, endeavoured to subdue at a blow our country and yours and the whole of the region within the straits; and then, Solon, your country shone forth, in the excellence of her virtue and strength, among all mankind. She was pre-eminent in courage and military skill, and was the leader of the Hellenes. And when the rest fell off from her, being compelled to stand alone, after having undergone the very extremity of danger, she defeated and triumphed over the invaders, and preserved from slavery those who were not yet subjugated, and generously liberated all the rest of us who dwell within the pillars.
But afterwards there occurred violent earthquakes and floods; and in a single day and night of misfortune all your warlike men in a body sank into the earth, and the island of Atlantis in like manner disappeared in the depths of the sea. For which reason the sea in those parts is impassable and impenetrable, because there is a shoal of mud in the way; and this was caused by the subsidence of the island.
There's no shoal of mud in the Atlantic Ocean, but there is low swamp land in the East Indies. Maybe after 9000 years the Mediterranean and the Indian Ocean were confused. The Indian Ocean would appear to be a large harbor because it's completely surrounded by land, except far to the south. The only entrance being the straits of the East Indies. No doubt if the Atlanteans invaded the Mediterranean Basin, they would invade via the pillars of Heracles, they being a maritime power and the Mediterranean may have not even existed 11,600 years ago as evidenced by the Black Sea flood account. Interesting that the acount describes an invasion of Asia too.
Find an area of the ocean that was unnavigable because of muddy shoals circa Plato's time and that should be a good candidate. Sounds like the East Indies if anything. The fact that there is a mud volcano near Cuba due to a possible subsidence of the land make them possible elsewhere there was a subsidence of land.
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.