A breakwater is a permanent structure constructed at a coastal area to protect against tides, currents, waves, and storm surges. Breakwaters have been built since Antiquity to protect anchorages, helping isolate vessels from marine hazards such as wind-driven waves. A breakwater, also known in some contexts as a jetty or a Mole, may be connected to land or freestanding, and may contain a walkway or road for vehicle access.
The Alamitos Bay, California, entrance channel. Breakwaters create safer harbours, but can also trap sediment moving along the coast.
Breakwater under construction in Ystad, Sweden (2019)
A breakwater in Haukilahti, Espoo, Finland
Barra da Tijuca – Rio de Janeiro
A jetty is a structure that projects from land out into water. A jetty may serve as a breakwater, as a walkway, or both; or, in pairs, as a means of constricting a channel. The term derives from the French word jetée, "thrown", signifying something thrown out.
Coastal lagoons fronted by barrier spits typically have entrances that migrate over time. Here, the entrance has been fixed by jetty construction. Carlsbad, California, April 1998.
Aerial view of a jetty at Swakopmund, Namibia (2017)
North Jetty on the left and South Jetty on the right at the mouth of Sebastian Inlet in Florida from the Indian River to the Atlantic Ocean.
Aerial view of jetties, constructed of dolosse, at Humboldt Bay harbor entrance. These jetties mitigate unpredictable shifting sands.
