An assembly of underwater bodies and a launcher therefor. The assembly is adapted for mounting on a submarine outside the pressure hull. The assembly includes a launcher having a housing for enclosing an underwater body, a body support structure within the housing for supporting the body, a pressure regulator system in communication with the housing for imposing a selected pressure on an interior of the housing, a hatch pivotally mounted on the housing, and an actuator for opening the hatch to permit the body to exit the hatch and for closing the hatch. The underwater body is a self-propelled body adapted to exit by gravity from the launcher. A release device is disposed on the launcher for releasing the body from the launcher to permit the exit of the body from the launcher by gravity. (4 figures)