Abstract: The hull of a docked ship is treated with apparatus which includes a frame which can move horizontally along the dock wall. The frame has vertical guides and a carriage is movably mounted along the vertical guides. The carriage carries a device for treating the ship's hull which includes a two-part arm, the first or upper portion of which is connected to one end of the carriage for pivotal movement in a horizontal plane about a vertical pivot. The second or lower arm portion is connected at one end to the upper arm portion for pivotal movement in the horizontal as well as the vertical plane about two right-angled pivots. At the other end, the lower arm has a bracket and platform arrangement on which the actual treating device is mounted for pivotal movement.