If you enter the water with your hands/arms first - like when you do a regular header into the water - it doesn't hurt at all.
It also gives me the goose bumps when watching him like that! Especially doing a back flip requires a lot of body control. Aaaaw I'm just soooo proud of him, I guess it's not too difficult to read that between the lines :-))
I see! ^_^ I can definitely tell that you're proud! And yeah, the back flip was really cool :)