Abstract: The underwater dive vehicle disclosed has a selectively energizable propulsion unit for forcible driving the vehicle through the water and at least one resilient gas filled buoyancy element which is in open contact with the surrounding water when the vehicle is in the water. The volume of the gas in the buoyancy element provides sufficient displacement of the water to keep the vehicle afloat at the surface when unattended or to support a diver. When the vehicle is submerged water pressure will act directly upon and tend to compress the resilient buoyancy element and the gas contained therein. This reduces the volume of the gas within the buoyancy element and thus reduces buoyancy of that element. Sealed housings such as those surrounding parts of the propulsion unit are filled with a non-conductive and non-corrosive liquid to prevent distortion and subsequent leaking of the seals, and non-moveable electrical components are encased in waterproof epoxy.