It depends on the snake. Some ball pythons are okay with water, and some are very AFRAID of water.

If you don't have a reason to soak your snake, then in my opinion, you shouldn't. There is no benefit for the snake for just randomly giving it a bath. If your snake has stuck shed or is a little backed up then a bath or soak is fine.

Now, IF you really feel the need to soak your snake, the water should be VERY SHALLOW. only a half inch to 1inch thick. These snakes are not the best swimmers (although they can swim somewhat) and they can drown in deep water.