Jetty

A structure projecting out into the sea, usually at the mouth of a harbor or river intersecting the coast, for the purpose of protecting a navigation channel or harbor, or to influence water currents; often built in pairs along both sides of an entrance channel.

Such a structure is generally built on an open coast extending into a body of water.

It is designed in a way that can prevent shoaling of a channel by littoral materials. It directs and confine stream or tidal flow.

In the Navigation Law it is defined as a structure located within the shorelines of a body of water for the purpose of controlling currents usually to prevent filling in of a channel.

Jetties are also built at the mouths of rivers or tidal inlets to help deepen and stabilize a channel.