A semi mythical dive site like this place would be interesting

That would be cool, I would love to dive something like that.

That looks like somewhere that Sgt_Brony's wreck would be found. What a cool discovery.

I think some underwater sci-fi dive sites would be cool too, maybe some ancient Prothean ruins, or a long-lost but still functional Stargate . . .

I was wondering whether somebody else had thought of underwater ruins (as opposed to shipwrecks). Apparently I'm much too late for original thoughts :(

How about Sunken R'lyeh? (I'm not proposing to include Deep Ones or Great Old Ones, just some cyclopean masonry).

We had the opportunity during community shipwreck. Sadly many people wanted same old