Abstract: An immersed prime mover device, typically of some few cubic inches or feet in volume, cyclically vents accumulated compressed air, typically 10-200 P.S.I. and more typically 90-110 P.S.I. derived from air compressors or from storage tanks, forcibly eject a slug of water, thereby producing a propulsive force. The accumulation may be some few cubic inches per minute in a large reservoir to but cyclically occasionally or infrequently eject the slug of water, producing an intermittent propulsive force. The accumulation may be of some substantial portion of the volume of an accumulation reservoir every few seconds, frequently cyclically ejecting the slug of water to produce a nearly continuous propulsive force.