True story: My dad was wreck diving (he was a SCUBA diver for 20+ years), working on a porthole to bring back to the surface, when he got bumped in the back. He thought it was his buddy trying to get his attention, so he ignored him for a second because he was getting low on air. He got bumped again. He turns around, and it's a big ass tiger shark. Luckily sharky was just curious, not hungry.