Jetty

A man-made structure, usually of concrete or stone, projecting into the water from the shore to protect a sandy beach from erosion, funnel current from an inlet, or protect a harbor or pier. Jetties may be constructed of wood and stone, or all stone, and form a perpendicular wall-like extension from a rocky or sandy shore into the water. They are primarily found in saltwater along the coasts.

Technically, a jetty is a structure that extends from inlets and harbor mouths. Its purpose is to protect those places by impeding wave and current action and to keep the entrance to them open for boat traffic; it is also meant to stabilize the beach or shoreline and help prevent erosion. Inlet and harbor jetties support various navigational aids.

Structures extending from a beachfront are technically called groins (see) but are commonly referred to as jetties. Groins are intended to impede the action of waves and current and to prevent erosion by stabilizing the sand in the immediate vicinity; they do not usually have navigational aids.

Jetties also exist on large bodies of freshwater, such as the Great Lakes, where they are primarily intended to aid boat passage and protect harbor entrances; freshwater jetties are often called piers (see), especially if they are topped with a surface that allows easy pedestrian access.

A jetty is slightly different from a breakwater (see) in that a jetty is usually narrower, shorter, and in some cases higher; it serves the same purpose, however. Some breakwaters are detached from shore, not accessible by foot, and may not be perpendicular to the beach or shoreline. Jetties always protrude above the water except under extreme water conditions, and they are a favored place for angling for diverse species.