The invention is a Self Propelled Underwater Device With Steerable Fin Stabilizer having a unique hull of generally tubular configuration and having a substantially conical shaped rear portion. The hull comprises a plurality of hollow interlocking tubular sections with one section including the rear portion; adjacent tubular hull sections include peripherally spaced apart threaded portions respectively disposed internally and externally thereof for mating relationship upon relative circumferential motion of the adjacent sections, the adjacent sections are further configured to provide an abutting joint when fully mated with watertight sealing means between the mated sections. The vehicle includes a plurality of steerable stabilization fins mounted on the hull about the rear conical portion at spaced apart locations with hull slots for receiving the respective fins when stowed. Common means pivot the fins out of said slots to extend generally perpendicular from said hull, and rotate each fin to steer the vehicle. Also, there is provided means for controlling the rotating means and a motor for driving a rear propeller.