Breakwater is a wall that protects a harbor, coast, or offshore structure from strong waves. Breakwaters also create a calm area where ships can anchor. Some breakwaters provide temporary protection while construction or mineral exploration takes place. Waves lose much of their energy as they strike a breakwater.
Some breakwaters are built as mounds of soil, rock, or concrete. Other breakwaters are built of sheet piles–that is, closely spaced planks of timber, steel, or concrete that are driven into the bottom of the lake or sea. In some cases, piles are placed in two rows and the space between them is filled with rocks. The kind of breakwater used depends partly on the condition of the lake or sea bottom. For example, a soft bottom might require the use of sheet piles. A firm bottom would probably support a mound. The design must also take into account the action of waves in the most severe storm expected over a long period.