防波堤 breakwater /ˈbreɪkwɔːtər/

Definition: A breakwater is a wooden or stone wall that extends from the shore into the sea and is built in order to protect a harbor or beach from the force of the waves.

Synonyms: sea wall, spur, mole, jetty

Example
1.The zigzag of harbour walls and breakwaters below the cliff were deserted.