Bearded dragon splashing in his bath?

I was giving my bearded dragon a bath in the sink when suddenly he swerves around, splashing and slapping his tail on the water. He seems fine in the bath; he doesn't try to get out. I think he actually tries to swim. (I'm going to upgrade him to the bath soon) But is that normal for a bearded dragon to splash around? His tail was shedding and parts of the shed were sticking out so I think that's what was bothering him.