I checked with him and he doesn't mind if I share his design.
This instructable assumes that you already have a helmet and a waterproof camera, so it's mostly about how to mount the camera on your helmet.
And the idea should work for anyone who likes to get out on the water and doesn't mind violating some sort of dress code of their sport. I'm thinking of surfers for instance and kite boarders and sail boarders, none of whom seem to wear helmets.
Step 1: Materials you will need
a foam block,
some bunji cord
and three cable ties, or lacking those, string or wire.