Zen Fly Fishing: Sting Rays Mating?

	This sight got my attention while I was walking past Phillip to fish the water North of him. They were not moving. I thought they were dead since they were belly-up, but I noticed that one was biting the other on the back of its wing.
	As soon as a wave surged in, they started writhing and undulating.
	They quickly got upright and started to flutter in the sand.
	Soon got back to water and started to swim off.
	The male swam off bumped into Phillip and got back to deeper water between his legs. I think they are Round Stingrays (Urolophus halleri). Mating is just a guess but what else could it be???