The leak sealer (10) for a ships hull (1) comprises a tube (11) whose end face (12) has an inflatable balloon (13) on it. The pipe is strongly attached to the balloon. The volume of the pipe and the volume of the balloon meet in a fluidic section. The diameter (25) of the pipe is small when compared to the diameter (35) of the inflated balloon. The inflated balloon (33) is put in the direction of the hull and has a circular cross-section and right angled head. The hull has the balloon built on it, lying around the boundary surface of the ship like an aerofoil section.
