Glossary of Nautical Terms - D

D

Daggerboard

A type of light centerboard that is lifted vertically; often in pairs, with the leeward one lowered when beating.

Davit

1. A spar formerly used on board ships as a crane to hoist the flukes of the anchor to the top of the bow, without injuring the sides of the ship.

2. A crane, often working in pairs and usually made of steel, used to lower things over the side of a ship, including launching a lifeboat over the side of a ship.

Davy Jones' Locker

An idiom for the bottom of the sea.

Day-blink

Moment at dawn where, from some point on the mast, a lookout can see above low lying mist which envelops the ship.

Day beacon

An unlighted fixed structure which is equipped with a dayboard for daytime identification.

Dayboard

The daytime identifier of an aid to navigation presenting one of several standard shapes (square, triangle, rectangle) and colors (red, green, white, orange, yellow, or black).

Dead ahead

Exactly ahead, directly ahead, directly in front.

Deadeye

A wooden block with holes (but no pulleys) which is spliced to a shroud. It is used to adjust the tension in the standing rigging of large sailing vessels, by lacing through the holes with a lanyard to the deck. Performs the same job as a turnbuckle.

Dead in the water

Not moving (used only when a vessel is afloat and neither tied up nor anchored).

Deadlight

A strong shutter fitted over a porthole or other opening that can be closed in bad weather.

Deadrise

The design angle between the keel (q.v.) and horizontal.

Dead run

See running.

Deadwood

A wooden part of the centerline structure of a boat, usually between the sternpost and amidships.

Decks

The top of the boat; the surface is removed to accommodate the seating area. The structures forming the approximately horizontal surfaces in the ship's general structure. Unlike flats, they are a structural part of the ship.

Deck hand or decky

A person whose job involves aiding the deck supervisor in (un)mooring, anchoring, maintenance, and general evolutions on deck.

Deck supervisor

The person in charge of all evolutions and maintenance on deck; sometimes split into two groups: forward deck supervisor, aft deck supervisor.

Deckhead

The under-side of the deck above. The inside of the boat is normally paneled over to hide the structure, pipes, electrical wires. It can be in thin wood planks, often covered with a vinyl lining, or in thin PVC or now even in fiberglass planks.

Decommission

To formally take (a naval vessel) out of active service, after which the vessel is said to be out of commission or decommissioned. Sometimes used less formally to mean taking a commercial ship out of service.

Depot ship

A ship which acts as a mobile or fixed base for other ships and submarines or supports a naval base.

Depth of hold

The height from the lowest part of the hull inside the ship, at its midpoint, to the ceiling that is made up of the uppermost full length deck. For old warships it is to the ceiling that is made up of the lowermost full length deck.

Derrick

A lifting device composed of one mast or pole and a boom or jib which is hinged freely at the bottom.

Despatch boat

Alternative spelling of dispatch boat.

Destroyer (originally torpedo boat destroyer)

A type of fast and maneuverable small warship introduced in the 1890s to protect capital ships from torpedo boat attack, since increased in size and capabilities to become a long-endurance warship intended to escort larger vessels in a fleet, convoy, or battle group and defend them against submarines, surface ships, aircraft, and missiles.

Destroyer escort

A smaller, lightly armed warship built in large numbers during World War II, cheaper, slower, and less-well-armed than a destroyer and designed to escort convoys of merchant ships or naval auxiliaries. Employed primarily for anti-submarine warfare, but also provided some protection against aircraft and smaller surface ships.

Destroyer leader

A large destroyer suitable for commanding a flotilla of destroyers or other small warships; a type of flotilla leader.

Devil seam

The devil was possibly a slang term for the garboard seam, hence "between the devil and the deep blue sea" being an allusion to keel hauling, but a more popular version seems to be the seam between the waterway and the stanchions which would be difficult to get at, requiring a cranked caulking iron, and a restricted swing of the caulking mallet.

Devil to pay (or Devil to pay, and no pitch hot)

"Paying" the devil is sealing the devil seam. It is a difficult and unpleasant job (with no resources) because of the shape of the seam (up against the stanchions) or if the devil refers to the garboard seam, it must be done with the ship slipped or careened.

Dhow

the generic name of a number of traditional sailing vessels with one or more masts with lateen sails used in the Red Sea and Indian Ocean region, typically weighing 300 to 500 tons, with a long, thin hull. They are trading vessels primarily used to carry heavy items, like fruit, fresh water or merchandise. Crews vary from about thirty to around twelve, depending on the size of the vessel.

Dinghy

1. A type of small boat, often carried or towed as a ship’s boat by a larger vessel.

2. Also a small racing yacht or recreational open sailing boat, often used for beginner training rather than sailing full-sized yachts.

3. Utility dinghies are usually rowboats or have an outboard motor, but some are rigged for sailing.

Directional light

A light illuminating a sector or very narrow angle and intended to mark a direction to be followed.

Dispatch boat

A vessel ranging in size from a small boat to a large ship tasked to carry military dispatches from ship to ship, from ship to shore, or, occasionally, from shore to shore.

Displacement

The weight of water displaced by the immersed volume of a ship's hull, exactly equivalent to the weight of the whole ship.

Displacement hull

A hull designed to travel through the water, rather than planing over it.

Disrate

To reduce in rank or rating; demote.

Distinguishing mark

A flag flown to distinguish ships of one seagoing service of a given country from ships of the country's other seagoing service(s) when ships of more than one of the country's seagoing services fly the same ensign.

Dock

1. In American usage, a fixed structure attached to shore to which a vessel is secured when in port, generally synonymous with pier and wharf, except that pier tends to refer to structures used for tying up commercial ships and to structures extending from shore for use in fishing, while dock refers more generally to facilities used for tying up ships or boats, including recreational craft.

2. In British usage, the body of water between two piers or wharves which accommodates vessels tied up at the piers or wharves.

3. To tie up along a pier or wharf.

Dockyard

A facility where ships or boats are built and repaired. Routinely used as a synonym for shipyard, although dockyard sometimes is associated more closely with a facility used for maintenance and basing activities, while shipyard sometimes is associated more closely with a facility used in construction.

Dodger

A hood forward of a hatch or cockpit to protect the crew from wind and spray. Can be soft or hard.

Doghouse

A slang term (in the US, mostly) for a raised portion of a ship's deck. A doghouse is usually added to improve headroom below or to shelter a hatch.

Dogvane

A small weather vane, sometimes improvised with a scrap of cloth, yarn or other light material mounted within sight of the helmsman. (See Tell-Tale)

Dog watch

A short watch period, generally half the usual time (e.g. a two-hour watch rather than a four-hour one). Such watches might be included in order to rotate the system over different days for fairness, or to allow both watches to eat their meals at approximately normal times.

Doldrums or equatorial calms

The equatorial trough, with special reference to the light and variable nature of the winds.

Dolphin

A structure consisting of a number of piles driven into the seabed or riverbed as a marker.

Dory or doree, dori, or (RN) dorey

A shallow-draft, lightweight boat, about 5 to 7 metres long, with high sides, a flat bottom and sharp bows. Traditionally used as fishing boats, both in coastal waters and in the open sea.

Double-shotted

The practice of loading smooth-bore cannons with two cannon-balls.

Downbound

1. A vessel traveling downstream.

2. Eastward-traveling vessels in the Great Lakes region (terminology as used by the St. Lawrence Seaway Development Corporation).

Downhaul

A line used to control either a mobile spar, or the shape of a sail. A downhaul can also be used to retrieve a sail back on deck.

Drabbler

An extra strip of canvas secured below a bonnet (q.v.), further to increase the area of a course

Draft or draught (both /ˈdrɑːft/)

The depth of a ship's keel below the waterline.

Dragon boat (also dragonboat)

One of a family of traditional paddled long boats of various designs and sizes found throughout Asia, Africa and the Pacific Islands. For competitive events, they are generally rigged with decorative Chinese dragon heads and tails. Dragon boat races are traditionally held during the annual summer solstice festival.

Dreadnought

A type of battleship designed with steam turbine propulsion and an "all-big-gun" armament layout in which the ship's primary gun power resided in a primary battery of its largest guns intended for use at long range, with other gun armament limited to small weapons intended for close-range defense against torpedo boats and other small warships. Predominant from 1906, dreadnoughts differed from earlier steam battleships, retroactively dubbed "predreadnoughts", which had only a few large guns, relied on an intermediate secondary battery used at shorter ranges for most of their offensive power, and had triple-expansion steam engines.

Dressing down

1. Treating old sails with oil or wax to renew them.

2. A verbal reprimand.

Dress overall

To string International Code of Signals flags, arranged at random, from masthead to masthead (if the vessel has more than one mast) and then down to the taffrail, on a ship in harbor as a sign of celebration of a national, local, or personal anniversary, event, holiday, or occasion. When a ship is properly dressed overall, ensigns fly at each masthead unless displaced by another flag – for example, that of a flag officer on board – in addition to the ensign flown in the usual position at the stern.

Drifter

A type of fishing boat designed to catch herring in a long drift net, long used in the Netherlands and Great Britain.

Driver

The large sail flown from the mizzen gaff.

Driver-mast

The fifth mast of a six-masted barquentine or gaff schooner. It is preceded by the jigger mast and followed by the spanker mast. The sixth mast of the only seven-masted vessel, the gaff schooner Thomas W. Lawson, was normally called the pusher-mast.

Drogue (/ˈdroʊɡ/)

A device to slow a boat down in a storm so that it does not speed excessively down the slope of a wave and crash into the next one. It is generally constructed of heavy flexible material in the shape of a cone. Also see sea anchor.

Drydock

A narrow basin or vessel used for the construction, maintenance, and repair of ships, boats, and other watercraft that can be flooded to allow a load to be floated in, then drained to allow that load to come to rest on a dry platform.

Dunnage (/ˈdʌnɨdʒ/)

1. Loose packing material used to protect a ship's cargo from damage during transport. (Also see #Fardage)

2. Personal baggage.