Squares off the Dry Tortugas

Just off the Dry Tortugas in Florida I see two squares here: 24.587646, -82.914549. Am wondering if this is just some kind of random Google Earth overlay, or is is something covered up? Why would they be here?

I'd like to think that the squares were hiding ample bosomed mermaids, sitting on treasure chests, resting on a graveyard of lost aircraft. But then good ol' Billy O comes along and reminds me that the least complicated explanation is probably more likely, and the two square are most likely just another of the numerous data errors found in the Google Earth imagery. Drat!

What I thought, thanks! Now browsing the archives...