sea anchor

A sea anchor (also known as a drift anchor, drift sock, para-anchor or boat brake) is a device that is streamed from a boat in heavy weather. Its purpose is to stabilize the vessel and to limit progress through the water. Rather than tethering the boat to the seabed with a conventional anchor, a sea anchor provides drag, thereby acting as a brake. Normally attached to a vessel's bows, a sea anchor can prevent the vessel from turning broadside to the waves and being overwhelmed by them.
Early sea anchors were crude devices, but today most take the form of a marine drogue parachute. These are so efficient that they need a tripping line to collapse the parachute for retrieval. Being made of fabric, a sea parachute may be bagged and easily stowed when not in use.
(A similar device to the sea anchor is the much smaller drogue, which is streamed from a vessel's stern in strong winds so as to slow the boat to prevent pitchpoling or broaching in an overtaking sea).

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