breakwater

A construction in or around a harbour designed to break the force of the sea and to provide shelter for vessels lying inside.

[…]there is a channel, some three miles wide between the city and the mainland, and some mile and a half wide between it and the sandy breakwater called the Lido, which divides the lagoon from the Adriatic,

But there's a pier or breakwater runs out into the sea just here, which we could defend longer than anything else, like Horatius and his bridge.

A low bulkhead across the forecastle deck of a ship which diverts water breaking over the bows into the scuppers.

A wooden or concrete barrier, usually perpendicular to the shore, intended to prevent the movement of sand along a coast.

A suburb of Geelong, Victoria, Australia