Momsen began to look for ways to rescue submariners. He conceived a diving bell, which could be lowered to a submarine in distress, mated to an escape hatch, and opened to allow trapped submariners to climb in. A watertight seal to the submarine could be achieved by placing a rubber gasket around the diving bell's bottom and reducing the air pressure once the bell was over the escape hatch. Then, the hatch could be opened, and the trapped submariners could climb aboard.