Davits - A set of arms on a ship from which its lifeboats are suspended.

Deadfreight - Non-utilization of cargo carrying capacity on a vessel.

Deadweight - Deadweight Tonnage (DWT) - The lifting or carrying capacity of a ship when fully loaded. This measure is expressed in long tons when the ship is in salt water and loaded to her marks. When loaded to her summer marks the value is for her summer deadweight (SWDT). It includes cargo, bunkers, water, (potable, boiler, ballast), stores, passengers and crew.
1 Long Ton = 2,204.6 lbs.

Deadweight Scale - A table that is part of the vessel plans and indicates the draft the vessel will be down to at any particular phase of loading.

Deck - A platform or horizontal floor that extends from side to side of a ship. The main deck is the highest complete deck on a ship (the one which runs the full length of the ship).

Deck Log - Also called Captain's Log, scrap logbook or rough logbook. A full nautical record of a ship's voyage, written up at the end of each watch by the deck officer on watch. The principle entries are: course steered; distance run; compass variations, sea and weather conditions; ship's positions, principal headlands passed; names of lookouts, and any unusual happenings such as fire, collision, and the like.

Deck Officer - As distinguished from engineer officer, refers to all officers who assist the master in navigating the vessel when at sea, and supervise the handling of cargo when in port.

Deck Stores - The spare gear and consumable stores provided for the upkeep and safe working of the tanker and her cargo, excluding stores used in engine room.

Deep Water Route - A designated area within definite limits which has been accurately surveyed for clearance of sea bottom and submerged obstacles to a minimum indicated depth of water.

Demise Charter- Also called bareboat charter in which the bare ship is chartered without crew; the charterer, for a stipulated sum, taking over the vessel with a minimum of restrictions usually for 10 or more years. See Bareboat Charter.

Demurrage - A fixed sum, per day or per hour, agreed to be paid for the detention of the vessel under charter at the expiration of laytime allowed.

Density - The density of a homogeneous substance is the ratio of its mass to its volume. The density varies as the temperature changes and it is usually expressed as the mass per unit volume at a specified temperature.

Absolute Density - The mass of a substance per unit volume at a specified temperature.

Relative Density - The ratio of the mass of a given volume of fluid to the mass of an equal volume of pure water at the same temperature and pressure. Relative density replaces the term "specific gravity".

Relative Density At 60° - Fluid relative density measured against water with both materials at 60 degrees F and reference pressure of 14.696 psia (or equilibrium pressure). Equivalent to "RD 60/60".

Deviation - A departure from a voyage pattern on either the forward or return leg of a voyage.

Dirty Ballast - Applies to the seawater used for ballast when it is contaminated with the remnants or residue left in cargo tanks that previously carried crude persistent refined oils.

Dirty Ship - Refers to tankers that have been carrying crude oil and heavy persistent oils such as fuel oil and dirty diesel oils.

Dispatch - The function of issuing voyage instructions or sailing orders to vessels. Also an agreed amount to be charged by terminals for prompt vessel turn around.

Dispatch Days - Days saved in the loading and discharge of a cargo vessel within the (lay) time allowed under the charter party. Note: Dispatch is not usually applied in the tanker business.

Displacement Tonnage - Expressed in tons it is the weight of water displaced by the vessel which in turn is the weight of the vessel at that time. The vessel's light displacement is the weight of the vessel only and the vessel's loaded displacement is the weight of the vessel and all cargo, stores, fuel, water, etc. on board.

Disponent Owner - Charterer who has sublet the vessel and is acting as the owner per the terms of the contract.

Double Bottom - A general term used for all watertight spaces contained between the outside bottom plating, the tank top and the margin plate. Double bottoms are usually sub-divided into a number of separate tanks and can be used to hold clean ballast, potable or boiler feed water, or fuel. They also provide a measure of protection for cargo tanks if bottom plating is damaged in the event of grounding. Chances of pollution may be diminished due to this protection.

Double Hulled - Hull construction design in which a tanker has an inner and outer side and bottom.

Double Sided - Hull construction design in which a tanker has an inner and outer side.

Draft - The depth of a ship in the water. This distance is measured from the bottom of the ship to the surface of the water. Draft marks are cut into or welded on the surface of a ship's plating. They are placed forward and aft on both sides of the hull and also amidships. At the midships draft we will also find the authorized Load Line markings which designate maximum drafts allowed for vessels under various conditions.

Dry Certificate - A document issued at the discharge port by a representative of the consignee indicating that each shipboard cargo tank has been completely discharged.

Dry-dock - An enclosed basin into which a ship is taken for underwater cleaning and repairing. It is fitted with water tight entrance gates which when closed permit the dock to be pumped dry. Also called gracing dock, gracing dry dock.