line of shoals trending northeast to southwest for 10 miles (16 km) at the entrance to the Strait of Dover from the North Sea and lying about 6 miles (10 km) off the Kent coast of England. The shifting sands form shelter for the anchorage of The Downs and are partly exposed at low water. They present a major hazard to navigation, however, and are frequently the scene of wrecks, in spite of lights and bell buoys.