Breakwater

A breakwater is a permanent coastal structure built to protect an anchorage or shoreline against tides, currents, waves and storm surges, isolating vessels from marine hazards such as wind-driven waves; breakwaters have been built since antiquity and may be connected to land or freestanding, sometimes carrying a walkway or road. As part of coastal management, breakwaters are installed parallel to a shoreline to reduce wave energy and erosion, and smaller versions built 100 to 300 feet offshore in shallow water protect gently sloping beaches, while a related structure called a groyne is placed perpendicular to the shore to slow the longshore drift of sediment. Notable historical examples include the rock breakwaters that enhanced the natural harbors at Plymouth Sound, Portland Harbour and Cherbourg, and the Mulberry harbours, mobile breakwaters towed into place during the 1944 Normandy invasion to create artificial harbors for the Allied landings.