Scratching At Water Bowl

Sometimes when Johnny drinks, he kinda scratches/knits at the water bowl WHILE drinking. Either on carpet, plastic or floor. Its not a problem for me, but I've always wondered just why he does it?

Cats do that. I suspect it's like an itch to play.

No clue, but unless he's drinking from the potty, Oliver does it too! (Yeah, I know that's kinda gross, but he throws a hissy fit if I close the potty and wont drink out of his other two bowls... even if he doesnt wanna drink from the potty at that moment, it has to be available) I've heard of kitties digging when they eat - like an instinct to cover and save any uneaten food - but I don't understand the water thing... I think it's cute and he's not destroying anything with his capped claws, so oh well... wonder if anyone's got an actual explaination for this...