Blue Lizard apparently makes an actual waterproof sunblock, though the link escapes me and my google-fu is too weak to find the description.
Apparently, the Australian definition of water proof is based whether it can stay on for hours in a hot tub.
From experience, the American definition of waterproof is simply based on whether the manufacturer prints it on the bottle, because there simply no even water resistant sunblock I have used. All require multiple applications to do anything, and none are anywhere near their numbers (30 times longer in the sun? Ha!)
But the people from cultures who value white skin (Japan, Korea, China, Philippines) have a different approach to keeping skin white that works even when traveling to warm places. Stay covered, obviously, but instead of worrying about excess sunscreen leaving the face white, actual go with multiple layers of foundation worn constantly. It will completely foul the silicone of the mask which means black skirted mask works best. And applying too much is, apparently, never an issue.
Get a black skirted mask with mirror lenses, and cover the rest with the above mentioned Kenny hood and it will do you for in the water.
But most of the time spent 'diving' is not in the water, (and light penetration is rather minimal in the water)so the hood and the mask are coming off, and really don;t make much difference anyway, and then you are back to mechanical protection (hats, rash guards, gloves, tights, shoes, and most importantly covered areas on boats), and applied protection (actual water proof sunscreen, and/or heavy foundation applied to all exposed areas.)