A winch mechanism of the surface compensating type for lifting objects from the surface of the sea comprises two or more variable pressure constant displacement hydraulic pump/motors coupled to drive a rope haulage mechanism; a pump connected for pumping operating fluid to the hydraulic pump/motors; a fluid accumulator branched from the high pressure fluid supply line from the pump to the pump/motors; and first and second non-return valves. The first non-return valve is in the high pressure fluid supply line between the fluid accumulator and the pump/motors to limit the flow of fluid from the accumulator to one only of the pump/motors, and the second non-return valve is between the high pressure fluid line and a low pressure fluid return line to permit the other pump/motor(s) to act as a pump.