Thanks for all the comments and the Daily Feature Jim!
When the tour groups left (25-40 off a boat) and I had this area to myself, or only a couple of other snorkelers that I kept my distance from, this was one of my most spiritual wildlife encounters. The turtles don't seem to be bothered by our presence. I tried to respect the 10 ft. rule, but often found them drifting right up to me (like the first shot). It was actually scary at first - there were a few quite large, and they are obviously powerful and can move fast when they want to, but they were very mellow. For the most part they seemed to just "hang out" or sleep on the bottom where they find a sandy spot next to some coral to slip under and jam themselves a bit, I never saw them eating anything. The photos were frosting on the cake.