Scuttling is the deliberate sinking of a ship by allowing water to flow into the hull. This can be achieved in several ways—seacocks or hatches can be opened to the sea, or holes may be ripped into the hull with brute force or with explosives. Scuttling may be performed to dispose of an abandoned, old, or captured vessel; to prevent the vessel from becoming a navigation hazard; as an act of self-destruction to prevent the ship from being captured by an enemy force (or, in the case of a vessel engaged in illegal activities, by the authorities); as a blockship to restrict navigation through a channel or within a harbor; to provide an artificial reef for divers and marine life; or to alter the flow of rivers.