Inspired by skimming stones on water, Barnes Wallis (UK) designed the bouncing bomb, first used on 16 May 1943, when Guy Gibson of the UK's 617 Squadron RAF released the cylindrical bombs in the Rhur Valley, Germany, during an attack on the Mhone and Eder dams. Following on from the experiments Wallis had done using a catapult and marbles in a tub of water, the bombs were dropped from a height of 18 m (60 ft), at a speed of 386 km/h (240 mph) and spinning at a rate of 500 rpm. The bombs then bounced over the water, sunk infront of the dam wall and exploded underwater. The result was heavy flooding in Germany, and also damaged production in the Ruhr Valley. Due to the low flying zone that was necessary to drop the bombs, the RAF sustained many losses interms of aircraft and personnel being brought down by German anti aircraft fire. Therefore, bouncing bombs were rarely used again.