Several different tracks here. If they are Greco-Roman and in the Mediterranean, they are nowhere near as large as they appear to be. They have to be small and from the looks of the seaweed near them, I'd say they are. And even if they're small, it would be fantastic that they survived intact as long as they have. Large ones would have broken apart hundreds of years ago. Great photo.
Reason why they are wherever they are? It's difficult to tell, but again, it has multiple possibilities. It almost looks like the statues are stuck in hardened lava, especially on the right lower side. That makes it possible that they were carried in a lava stream. In the area speculated, off Vesuvius? OR victims of a shipwreck that fell to the bottom?
The faces on the statuary don't look like typical Greek or Roman work. As a matter of opinion, it looks like the one farthest up could be one of the "Terra Cotta Warriors" of China. But then that challenges the size arguement. Hmmm.
I'm intrigued. I hope this isn't a silly joke. I want to KNOW! C'mon Rich...
