Once, when I was diving on the outer reef line in Broward just north of the Hillsboro inlet, I had a turtle literally swim up to me and bump the glass on my mask. It was a little disconcerting, especially since it was a BIG male loggerhead, and it actually pushed me back with its little friendly bump. I was doing some data collection on that particular dive, and the turtle actually followed me about for a bit! I have no idea whats its reason for this was, since it left the other two divers alone the entire dive. They were both convinced that the turtle was trying to get some action....
I do know that if you dive EPCOT they say that when the turtles are heading to the surface they don't care whats above them, and they will just push it aside it its between them and fresh air. So it is very likely it just didn't give a hoot there was a person there!
I've been "attacked" by sea turtles a number of times, with the majority of them occurring when egg counting during an arribada. Silly turtles quite literally walked over me as I had my head stuck in an hole watching eggs drop! Guess it was my fault for laying down on their beach, but who knew they would be so rude?