The New York Times' Eric Taub profiles the Liquad Image Underwater Digital Camera Mask - a diving mask with a built-in digital camera and camcorder. Think of it as a waterproof camcorder meets a helmet cam.
The Digital Camera Mask's quality didn't much impress Taub - and since it only records at 20 frames per second that's not surprising - but it does address a major deficiency with many waterproof camcorders on the market: how to view the footage you're recording underwater while you're recording it. You'll either have to wear goggles yourself or brave the chlorine or salt against your bare eyes. At least with the Digital Camera Mask, your eyes can stay alert for sharks while the camcorder does its thing.