Chief Mate CoC key terms

A navigation mark, often a red and white vertical striped buoy with a red spherical topmark, placed at the seaward edge of a channel to show where navigable water begins and the fairway can be safely entered.

The international set of rules for buoy shapes, colours, topmarks and lights, split into Region A and Region B, so that lateral marks consistently show the preferred side of a channel to follow.

Two aligned beacons or lights, the front one lower than the rear, that indicate a safe track along a channel by day and by night, and warn the navigator when the vessel drifts off the line.

A radar navigation technique in which the range of a fixed feature is monitored against a plotted line to give a continuous, instant check that the vessel is holding its planned track and cross-track error.

The vertical distance between the deepest point of the hull and the seabed at a given place and time, calculated from charted depth, tide height, vessel draft and an allowance for squat and swell.

The loss of under-keel clearance caused by water flow around a moving hull, greatest in shallow water and at higher speed, producing a bodily sinkage and often a change of trim by the bow.

The interaction between a moving hull and a nearby bank or channel side, which can suck the vessel toward the bank and swing the bow away, worsening in narrow or shallow channels.

The distance between a vessel's centre of gravity and its transverse metacentre. A positive value gives initial stability and a righting moment when heeled; excessive values cause a stiff, uncomfortable roll.

The horizontal distance between the centre of gravity and the centre of buoyancy at a given angle of heel, whose product with displacement gives the righting moment. It is plotted to form the stability curve.

The apparent rise of a vessel's centre of gravity caused by liquid moving freely in partially filled tanks, which reduces effective metacentric height and can make a stable ship behave as if unstable.

The angle at which a vessel with negative initial metacentric height comes to rest, because the centre of buoyancy shifts until it lies vertically below the centre of gravity. It can be corrected by filling low tanks.

Compensation payable by a charterer to the shipowner when the charterer fails to supply the full quantity of cargo agreed for loading, calculated on the shortfall at the agreed rate.

Liquidated damages payable by the charterer for detaining a vessel beyond the laytime allowed for loading or discharging, at a daily rate fixed in the charter party.

The period agreed in a charter party within which the charterer must complete loading or discharging. Once it expires, time becomes chargeable as demurrage unless an exception applies.

A written statement that the vessel has arrived at the agreed place and is in all respects ready to load or discharge, with its tender starting laytime subject to the terms of the charter party.

A long-standing rule of maritime law under which a sacrifice or expense deliberately made to save ship and cargo from a common peril is shared proportionately between the owners of all the property saved.

Damage to or loss of a ship or cargo caused by an insured peril that is borne by the owner of the affected property alone, rather than being shared among all parties as in general average.

The voluntary assistance given to a vessel or property in peril at sea, which entitles the salvor to a reward under the no cure, no pay principle or under the SCOPIC clause.

A supplementary agreement to a Lloyd's salvage contract that guarantees the salvor a tariff-based payment for services and equipment, with the reward otherwise assessed under Article 13 of the Salvage Convention.

The coating or treatment applied to a hull to prevent the attachment of marine organisms. Its use and removal are regulated by the AFS Convention, which bans harmful organotin compounds such as TBT.

The process of treating or exchanging ballast water to reduce the transfer of invasive aquatic species, governed by the Ballast Water Management Convention and recorded in a dedicated ballast water record book.

The accumulation of algae, barnacles and other organisms on submerged surfaces of a hull, which increases drag and fuel consumption and is a pathway for transferring invasive species between regions.

The part of the MARPOL Convention dealing with pollution by oil, setting rules for oily water discharge, the Oil Record Book, and the construction and equipment of oil tankers.

A mandatory record, kept on board and available for inspection, of all oil transfers, discharges, disposal operations and machinery space bilge movements, used to verify compliance with MARPOL Annex I.

The part of MARPOL covering air pollution from ships, including sulphur and nitrogen oxide limits, emission control areas, ozone-depleting substances, and the energy efficiency and carbon intensity rules.

A designated sea area under MARPOL Annex VI where stricter limits apply to sulphur oxides, particulate matter or nitrogen oxides, requiring low-sulphur fuel, an exhaust gas cleaning system or another approved method.

A mandatory log recording every discharge, incineration or landing ashore of ship-generated garbage, used by port state control to verify compliance with MARPOL Annex V.

The rule stating that any vessel coming up from more than 22.5 degrees abaft the beam of another is overtaking, and must keep clear until finally past and clear, regardless of the other vessel's type.

The rule requiring two power-driven vessels meeting on nearly reciprocal courses, with risk of collision, each to alter course to starboard so that they pass port to port.

The speed at which a vessel can take proper and effective action to stop within a distance appropriate to the prevailing circumstances, visibility, traffic density, draft and stopping ability.

Any condition in which visibility is reduced by fog, mist, falling snow, heavy rain or other causes, requiring sound signals, a safe speed and readiness to stop under COLREG Rule 19.

The prescribed sound signal, such as one prolonged blast at intervals for a power-driven vessel making way, used in or near restricted visibility to warn other vessels of position and movement.

An intense low-pressure system over warm tropical seas with a closed circulation around a calm eye, known by regional names such as hurricane, typhoon or cyclone, whose path must be avoided by evasive routing.

A rule stating that in the Northern Hemisphere, with your back to the wind, low pressure lies to your left and high to your right; the reverse applies in the Southern Hemisphere.

The path followed by the centre of a low-pressure system as it moves, forecast from synoptic charts and model guidance so that the bridge team can plan a safe route around it.

The condition in which watertight doors, hatches, vents and closures are kept closed or properly secured so that flooding is contained within the compartment where it occurs.

A watertight bulkhead near the bow, required by SOLAS to be positioned within a specified distance from the forward perpendicular, designed to limit flooding after a bow collision.

The planned organisation of crew, equipment and procedures to contain flooding, fight fire and preserve stability after an incident, including boundary cooling, shoring and the use of damage control plans.

The International Ship and Port Facility Security Code, which sets minimum security measures for ships and port facilities through ship security plans, security levels and designated security officers.

The documented system required by the ISM Code, covering procedures, responsibilities and resources so that the ship is operated safely and pollution is prevented, verified by audit and certification.

A document, posted throughout the ship, assigning every person on board a specific station and duty for emergencies such as fire, abandon ship or man overboard, with substitutes for key roles.

A joint committee of management and crew representatives that meets regularly to review safety matters, accidents and near misses, and to recommend improvements to the safety management system.

A management approach in which honest errors are treated as learning opportunities rather than grounds for punishment, while deliberate breaches and reckless behaviour are still dealt with firmly.

The systematic control of hours of work and rest, watch schedules and workload to reduce the likelihood that tiredness impairs a seafarer's performance, as required by the STCW and MLC frameworks.