Anchor

An anchor is a heavy object, often made out of metal, that is used to attach a ship to the bottom of a body of water at a specific point. There are two primary classes of anchors—temporary and permanent. A permanent anchor is often called a mooring, and is rarely moved; it is quite possible the vessel cannot hoist it aboard but must hire a service to move or maintain it. A temporary anchor is usually carried by the vessel, and hoisted aboard whenever the vessel is under way; it is what most non-sailors mean when they refer to an anchor. A sea anchor is a related device used when the water depth makes using a mooring or temporary anchor impractical. The hole through which an anchor rope passes is known as a hawsepipe[1].

An anchor works by resisting the movement force of the vessel which is attached to it. There are two primary ways to do this — via sheer mass, and by "hooking" into the seabed. It may seem logical to think wind and currents are the largest forces an anchor must overcome, but actually the vertical movement of waves develop the largest loads, and modern anchors are designed to use a combination of technique and shape to resist all these forces.

An interesting element of anchor jargon is the term aweigh, which describes the anchor when it is hanging on the rope, not on the bottom; this is linked to the term to weigh anchor, meaning to lift the anchor from the sea bed, allowing the ship or boat to move. An anchor is described as aweigh when it has been broken out of the bottom and is being hauled up to be stowed. Aweigh should not be confused with under way, which describes a vessel which is not moored to a dock or anchored, whether or not it is moving through the water. Thus, a vessel can be under way (or underway) with no way on (i.e., not moving).