This application concerns a method and system using a hydrodynamical effect for producing a potential over a body. The force obtained this way is useful for the propulsion and maneuvering of ships, submarines, aeroplanes, and airships. A body immersed in a fluid at rest is subject to equal pressures on all sides. A stream close to one side of the body will reduce the local pressure and produce a potential over the body. This is currently done by moving the body in the fluid, cf. aeroplane wings. The potential may be produced by setting up a stream or streams over one side of the body. Bodies attached to aeroplanes by hinges are useful for their lift, propulsion and maneuvering, and will make them independent of velocity for lift and maneuvering. The same will be the case for submarines. Airships and seagoing vessels may be designed so as to have their propulsive bodies integrated in their form. The streams are produced from nozzles, holes, or slits in tubes placed near the stagnation line of each body, thus defining its leading edge. Used on a ship, this technique lowers its bow wave and removes the dynamical losses connected with screw propulsion. The maneuvering force and precision are enhanced.