Skip bombing was a low-level bombing technique independently developed by several of the combatant nations in World War II, notably Italy, Australia, Britain, and the United States. It allows an aircraft to attack shipping by skipping the bomb across the water like a stone. Dropped at very low altitudes, the bomb never rises more than about 5 metres (16 ft) above the surface of the water, ensuring that it will hit the side of the ship as long as it is aimed correctly.