Abstract: The invention relates to a gas-driven pulsating water jet propulsive duct drive for watercraft with a propulsive duct which has at the front end an inlet aperture for water with a closure member closing and opening periodically by means of a drive device, is open at the rear end for ejection of water and comprises at the front end a power gas outlet behind the inlet aperture. With propulsive duct drives of this kind the forward inlet aperture of the water-filled propulsive duct is periodically closed, the power gas outlet opened, in order to feed power gas under pressure into the propulsive duct and to expel the fluid filling of the propulsive duct rearwards, the power gas outlet is closed and the forward inlet aperture opened again for a fresh fluid filling.