Underwater HDSLR video isn't the norm, so I thought I'd post this. It's from Backscatter, a company providing professional housing units for underwater video and still photography. They have a unit for the Canon 5D for (GULP!) $2,899. For my underwater shot in Rejouer, I used an underwater camera bag. It proved to be very buoyant and my DP struggled to keep it submerged, but it was only for one shot. Here's a tip my DP gave me, before shooting place a roll of toilet paper in the underwater housing unit then submerge it. If the toilet paper is wet you've got a leak in the housing unit.