Sea anchor
Modern commercial sea anchors are usually made of cloth, shaped like a parachute or cone, and rigged so that the wider end leads and the narrower end trails. When deployed, this type of sea anchor floats just under the surface, and the water moving past the sea anchor keeps it filled. Some varieties are cylindrical, with an adjustable opening in the rear that allows the amount of braking to be adjusted when deployed.
Anchor modeling
Anchor tables contain a single column in which identities are stored. An identity is assumed to be the only property of an entity that is always present and immutable. As identities are rarely available from the domain being modeled, they are instead technically generated, e g from an incrementing number sequence.