A torpedo launch system for a marine vessel includes an impulse tank connected via a straight water inlet tube to an inlet orifice in an outer casing of the vessel. A launch tube extends through the impulse tank to the outer casing, and through a pressure hull of the vessel to terminate at a rear door. Pressurized water is provided to the launch tube to launch a torpedo by mounting an impeller in the impulse tank. The impeller pumps water into the impulse tank to develop a pressure which is transmitted to the launch tube when a valve in the impulse tank is opened. The impeller is driven by a motor which receives power via cables which pass through the pressure hull. The impulse tank and motor are between the outer casing and the pressure hull.