Dredging is an excavation activity usually carried out underwater, in harbors, shallow seas, and freshwater areas with the purpose of gathering up bottom sediments to deepen or widen the sea bottom or sea channel. The dredging technique is often used to keep waterways and ports navigable and create an anti-sludge pathway for boats. It is also used as a way to replenish sand on some public beaches, where sand has been lost due to coastal erosion