A submerged breakwater is a breakwater whose upper part is below the average water level.
The most common coastal structures, such as a sand arrester and training dike, are breakwaters built parallel to the coast as coastal conservation facilities.
The purpose is to attenuate the energy of the wave at once by this submerged breakwater on the shore where a wave attack is strong to facilitate the defense of the coast itself, and to alleviate the erosiveness of the wave by smoothing the gradient of the wave that goes over it. It is also built to reduce public costs, avoid rapid seafloor fluctuations, and preserve the existing landscape.