Lets assume that in antiquity an advanced civilisation like that of the Roman Empire existed on a sizeable island the size of Spain in the middle of the Atlantic Ocean.
This civilisation built large monuments such as acropoles, temples, pyramids, shipyards, palaces and other public buildings across the island. These where constructed from materials such as marble, stone and concrete.
In my particular version of the Atlantis story, the island undergoes the same cataclysm as described in Plato's Critias ie:
But at a later time there occurred portentous earthquakes and floods, and one grievous day and night befell them, when the whole body of your warriors was swallowed up by the earth, and the island of Atlantis in like manner was swallowed up by the sea and vanished; wherefore also the ocean at that spot has now become impassable and unsearchable, being blocked up by the shoal mud which the island created as it settled down.
The only difference being the island sunk around 1000BC as opposed to Critias's 9,000 years before his lifetime.
My knowledge of geography, geology and oceans in general are limited, but i want to know, suppose in the year 2015 AD, a group of archaeologists begin an underwater expedition in state-of-the-art submersible vehicles to the area where Atlantis once was, what is the most likely state they would find these ancient monuments in? could they still be standing?
If not, then what kind of cataclysm could i describe that would cause the island to sink but the buildings to remain relatively intact? given that this is a story primarily about exploring an ancient submerged civilisation.