Dredging is an excavation activity or operation. It is usually carried out at least partly under water in shallow seas or fresh water areas with the purpose of gathering and lifting up bottom sediments to be disposed at different locations. This technique is often used to keep waterways navigable.
Dredging is also carried out to replenish sand on some public beaches, where the sand has been depleting due to coastal erosion. A dredger is the term used for any device, machine, or vessel which is used to excavate and remove material from the bottom level of a body of water.
In citing an example, a scoop attached to the end of a rope or pole by which a man can draws ediments up from the bottom of a pond is a dredger. Developing this idea further, a motorised crane equipped with a drag-bucket or clamshell (grabber) that is used to scoop material from thebottom of a body of water is also a dredger.