Some cats like to play with water bowls--they are not afraid of water. Cats don't have the greatest sight or depth perception when something is directly in front of them. So with a bowl of clear water it can be difficult for a cat to judge where the water line begins.
Cats can't tell where the level of the water is unless it's moving, so they either paw it or move the water bowl. Some cats will drink water by dipping their paw in it and then licking the water off of the paw. There is no "solution" to this behavior. I suggest putting a mat under the water bowl.
Professional Pet Sitting Services offered in the Upper to Mid-Pinellas County Area