Plenty of people use DSLR cameras for video. Most of these devices are not designed to be used underwater though. The AquaTech Sport Housing lets you take your camera to a depth of 33 feet. It has a Polyurethane construction and tactile controls. The aluminum parts are anodized for better protection.
The AquaTech Elite GH4 has an interchangeable port system and a standard tripod mounting point. It weighs 1.6kg. This particular version is compatible with the Panasonic GH4 and GH3.