That's odd because I always see all of my snakes do it. Even before the tubs, when they where in glass, and they had damp towels on the top of their tanks... they would still soak in the water dish. None of them have ever had mites, or parasites or anything like that to my knowledge, and I use a white substrate so i'm sure I would see them if they did have them. I just can't figure it out... I always just assumed that this was natural ball python behavior.