His croc experience taught him a bad habit. You may be able to jump on top of a croc but you never get over a stigray. That is wherre the barb is. I know divers who have been nicked that way but they were not right on top of the ray, only swiming close to the bottom. It appears Steve came right over top of the ray from behind trying to stay in the shot. The rule is you always swim under a ray. When they spook they throw up the barb and jump straight up, then out. That is how they get off the bottom where they lay and get going.
BTW it is really pretty cool to swim with the rays in the Caymans but the guides give you the same warning before you get in the water.
