We do something similar to kimbaz - water only about 5cm deep so Angus can lie flat on the bottom. We used to put a face washer under his head but now he kicks and splashes so much that he slides about (doesn't worry him but ocncerns me) that I've got a non-slip mat underneath him. I can wash his hair and body while he's amusing himself splashing. He enjoys it so much that he hasn't had a shower with Dh for ages (he used to like that too).