Plenty of people use DSLR cameras for video these days. If you plan to use your camera to capture video underwater, you are going to need the right kit. The Ikelite Underwater Camera Housing can help. It is rated to a depth of 200 feet and gives you access to all camera functions.
This underwater housing has a clear polycarbonate construction and mechanical controls. You also get an aluminum tray with rubberized right and left-hand grips and can attach additional accessories to the unit easily. The above video shows what you get.