Glossary of maritime terminology

Davits are two radial cranes on a ship which hold, lower and lift the lifeboats.

The Day of the Seafarer is an annual day of observance which was implemented by the International Maritime Organization (IMO) to recognise the contribution that seafarers make to the global supply chain and everyday life. It is celebrated on the 25th June.

Deadweight tonnage (DWT) is a means of measuring how much weight a vessel can carry so that the maximum weight can be determined. DWT is the sum of the weight of the cargo, crew, fuel, water (fresh and ballast), provisions, and passengers (if there are any.)

The deck is the name given to the various stories or levels of a boat or ship. The deck is a central construction which acts as a type of floor or ceiling - depending whether you are above or below it - within the vessel’s hull. However ‘deck’ is a generic shipping term and everything from yachts to container ships have different types of decks which have different names and are located in different places and at different levels onboard.

A deck barge carries oversize and/or heavy freight, such as project cargo, vehicles and machinery, that is transported on its top deck as opposed to inside a hold. 

Almost any vessel, whether it’s a cruise ship, an oil tanker, a military vessel, a general cargo ship, a ferry, or a heavy load carrier will count a Deck Cadet amongst her crew. A Deck Cadet is like an apprentice or a trainee seafarer. Typically a Cadet will help with daily operations and ship maintenance. Deck Cadet duties will also normally include assisting with preparations for departure and arrival at port.

If a Cadet is working in seafarer jobs in the merchant navy, this will include helping to supervise the loading and unloading of cargo, as well as its storage onboard. On a cruise ship or ferry, instead of cargo, a Cadet will assist in ensuring that passenger onboarding is safely and efficiently carried out. They will also learn how to moor the vessel.

A deck crane on a ship, as the name suggests, is a deck-mounted crane which is used for the loading and unloading of cargo. Commonly found on general cargo ships, container ships and bulk carriers, amongst others, deck cranes may be fixed rotary cranes, mobile rotary cranes or gantry cranes.

Deck equipment, also referred to as deck machinery, is the name given to anything on the deck of a vessel that is used when anchoring or berthing. This includes, but is not limited to, anchors, windlasses,  winches, steering gear, capstans, and other miscellaneous machinery.

Deck machinery, also referred to as deck equipment is the name given to anything on the deck of a vessel that is used when anchoring or berthing. This includes, but is not limited to, anchors, windlasses,  winches, steering gear, capstans, and other miscellaneous machinery.

A Deck Officer is an officer working in the deck department on a vessel - such as a Third Officer, Second Officer or Chief Officer. They assist the Master in navigational duties and supervise cargo handling when in port.

A seafarer who works on the deck of a ship and in the wheelhouse. The Deckhand is an entry level job on a vessel and they will take orders from higher ranks particularly the duty officers during navigation and maneuvering.

A deckhouse is a small superstructure (a part of the ship that is above its main deck) on a vessel’s top deck which contains the helm (a wheel or lever that controls the rudder) as well as other navigational instruments. 

Delta stands for the letter D in the International Radiotelephony Spelling Alphabet, which is most often referred to as the NATO Phonetic Alphabet or simply the Phonetic Alphabet. This is the most commonly used group of code words used to clearly communicate the letters of the Roman alphabet, particularly over the radio and is essential in helping seafarers give and receive messages, orders and instructions clearly and correctly.

Demurrage is a freight term that refers to the fine payable to the owner of a vessel by a supplier or port for failing to load or unload the ship within the time agreed as per the contract.

A derrick is a type of crane found onboard merchant ships.

A diesel generator, also known as a diesel generator engine, or a marine diesel generator serves the purpose of providing electrical power to a vessel’s electrical systems including lighting and the propulsion system whilst at sea.

They are a hybrid of an electric generator and a diesel engine and are specially designed to function in, and withstand, the specific environmental conditions that ships work in, including heavy vibrations, seawater and the salty sea air.

A diesel generator engine, also known as a diesel generator, or a marine diesel generator serves the purpose of providing electrical power to a vessel’s electrical systems including lighting and the propulsion system whilst at sea.

They are a hybrid of an electric generator and a diesel engine and are specially designed to function in, and withstand, the specific environmental conditions that ships work in, including heavy vibrations, seawater and the salty sea air.

Disabled ship: A ship is deemed disabled if it is found to not be seaworthy and safe or able to sail efficiently. This could be due to anything from not enough crew members or officers, engine problems, damage to the vessel’s gear, or even to the vessel itself.

The discharge port is any port where a vessel unloads its cargo.

A diving support vessel, often abbreviated to DSV, is a ship that is kitted out with specialized equipment for underwater operations including diving, inspection, repair and maintenance. It is often used in the oil and gas industries as well as in other sectors.

In maritime terminology, the word dock has two meanings.

Verb: To dock a ship - i.e. to bring a vessel into a port or harbor to moor it in its berth.
Noun: The ship sailed into the dock. A dock is a structure that has been built so vessels can come ashore and load or unload cargo or passengers.

Dockage is a fee levied by a port authority for the length of water frontage used by a vessel that is moored at a wharf.

A dolphin, or mooring dolphin, is a collection of pilings clustered together to which a ship or boat ties their lines to moor. They are also used to offer protection alongside a dock or the shore, or in a waterway. Some dolphins may be used as a base for navigational aids and some may also be used to stabilize a bridge or dock.

The domestic seawater system on a ship (also called the sanitary system), is a system that is primarily used to flush the toilets onboard. The system is made up of a hydrophore tank - a compressed  air pressurized tank - that stores and pumps seawater through the toilets.

A doppler speed log is an instrument used to measure the speed of a ship through the water. Using the Doppler Effect, which is simply put, the change in wave frequency during the relative motion between a wave source and its observer. By knowing the value of the transmitted frequency and the velocity of sound in the water and then measuring the received frequency, this can then be converted into speed to determine how fast the ship is moving.

The draft, in maritime terms, is the depth of a loaded ship in the water. The measurement is taken from the level of the waterline to the lowest point of the hull.

Drag is the term used when a ship is moving despite being anchored. The anchor is dragging along the sea bed. This is something the crew member on anchor watch should be looking out for at all times.

Noun: A dredge is either a hydraulic or mechanical machine that removes the accumulation of silt (fine sand and clay) from the bottom of a river or harbor. This is both for safety reasons, and to allow deeper vessels to use the waterway or harbor. Verb: The act of removing the accumulation of silt.

A dredger is a type of boat that is equipped with a tool, called a dredge, that draws, sucks, excavates or scrapes sediment such as sand, silt, gravel, trash, rocks, debris and animal and plant matter from the ocean floor, sea bed, lakes or a waterway such as a river, estuary or canal. The materials moved are then placed elsewhere or disposed of in an act known as dredging.

Dredging is the act of removing sediment particularly silt (sand clay and mud) from river or harbor bottoms. This is done both so that deeper vessels can use the area and for safety reasons.

Drift can mean one of two things in a nautical sense: 1) for a vessel to float with the wind or current and 2) the distance a boat is carried by a current during a given time.

A drillship (sometimes written drill ship) is a merchant vessel designed for scientific drilling purposes or for use in the exploratory offshore drilling of new gas and oil wells in deep waters.

They are large, self-propelled vessels that are equipped with drilling equipment and a derrick - a tall, lattice-type tower which is used to dig a hole for an oil well before then pushing the drill pipe deep into the sea bed.

Dry bulk cargo is unpackaged cargo that is stored in loose piles for transportation. Such as grains, nuts, cement, sand, minerals and wheat.

Dry cargo is cargo that is carried in bulk that is dry and not liquified.

More commonly called a bulk carrier or bulker, a dry cargo ship is a vessel that carries bulk cargo that is dry and not liquified.

A Dry dock is a narrow, enclosed basin or vessel into which a ship can be floated for construction, maintenance, cleaning and repair. Dry docks are fitted with watertight gates so that the dock can be pumped dry when the gates are closed.

DSV is an abbreviation of diving support vessel. This is a ship that is kitted out with specialized equipment for underwater operations including diving, inspection, repair and maintenance. DSVs are often used in the oil and gas industries as well as in other sectors.

Dunnage is any kind of packing material that is used as a protective filler inside a shipping container, box, or carton etc. to prevent movement and therefore damage to the cargo during shipping. Dunnage can be anything from wood to bubble wrap and from packing peanuts to inflatable air bags.

Duty is a government tax on imported merchandise.

DWT stands for deadweight tonnage (or dead weight tonnage). It is a means of measuring how much weight a vessel can carry so that the maximum weight can be determined. DWT is the sum of the weight of the cargo crew fuel water (fresh and ballast) provisions and passengers (if there are any.)

Hotel stands for the letter H in the International Radiotelephony Spelling Alphabet, which is most often referred to as the NATO Phonetic Alphabet or simply the Phonetic Alphabet. This is the most commonly used group of code words used to clearly communicate the letters of the Roman alphabet, particularly over the radio and is essential in helping seafarers give and receive messages, orders and instructions clearly and correctly.