Ships and Boats Industry Terminology

AIS (Automatic Identification System)

A VHF-based transponder system that continuously broadcasts a vessel’s identity, position, course, and speed to enhance situational awareness, collision avoidance, and traffic monitoring; mandatory for most SOLAS ships.

-Confirm the AIS transponder is broadcasting Class A. -Ops will geofence the anchorage using AIS targets. -We reconciled port call times against AIS tracks for the KPI report.

Alternative Fuels

Non-conventional marine fuels such as LNG, methanol, ammonia, biofuels, hydrogen, and e-fuels used to reduce emissions or comply with environmental rules; each has distinct energy density, safety, and infrastructure implications.

-The owner ordered methanol-ready engines for the newbuild. -We’re evaluating ammonia bunkering safety cases. -Shifting to a B30 biofuel blend cut our CO2 by roughly 20%.

Ballast Water Treatment System (BWTS)

Onboard equipment that disinfects or filters ballast water to kill or remove invasive organisms so discharges comply with the IMO Ballast Water Management Convention and, where applicable, USCG rules.

-The UV-based BWTS passed its commissioning test. -USCG type approval was a contract requirement. -We scheduled BWTS filter maintenance during dry dock.

Bunkers

Marine fuels consumed by a ship (e.g., VLSFO, MGO, LNG); also refers to the refueling process (bunkering), procurement strategy, quality control (ISO 8217), and associated logistics and risk management.

-We fixed 500 MT of VLSFO in Singapore. -Bunker hedging smoothed our fuel cost volatility. -The charterer pays for bunkers under a time charter.

CII (Carbon Intensity Indicator)

An IMO operational metric that rates a ship’s CO2 emissions per transport work (A to E annually) and pushes continuous efficiency improvements via speed, routing, and technical measures.

-The vessel slipped from C to D on CII last year. -We’ll slow steam to improve the CII rating. -Trim optimization helps our annual CII score.

Classification Society

An independent organization (e.g., ABS, DNV, LR, BV, RINA) that sets technical standards for ship design, construction, and maintenance, performs surveys, and issues class certificates required by insurers and many flag states.

-DNV is the class society for this tanker. -We must complete the Intermediate Survey to maintain class. -The retrofit requires class-approved drawings.

Deadweight Tonnage (DWT)

The total carrying capacity of a ship in metric tons, including cargo, fuel, freshwater, stores, crew, and passengers, but excluding the ship’s own lightship weight.

-She’s a 63,000 DWT Ultramax. -We’re cargo-limited, not DWT-limited on this leg. -Adding stores reduces available DWT for cargo.

Draft (Draught)

The vertical distance from the keel to the waterline; determines canal, port, and berth access and must account for squat, tide, and under keel clearance.

-Max draft at berth is 12.5 m. -We’re trimming by the stern to reduce propeller emergence. -Pilot requested a draft survey before sailing.

ECDIS (Electronic Chart Display and Information System)

An IMO-compliant electronic navigation system that displays official vector charts (ENCs), integrates sensors (GPS, AIS, radar), and supports route planning and monitoring, replacing most paper charts on SOLAS ships.

-Switch to the backup ECDIS and load updated ENC permits. -We’ll run a route check on ECDIS before departure. -Type-specific ECDIS training is mandatory.

EEXI (Energy Efficiency Existing Ship Index)

An IMO technical efficiency standard for existing ships that sets a required carbon-efficiency level; compliance often achieved via power limitation, propulsion upgrades, or other technical modifications.

-We’ll install an Engine Power Limiter to meet EEXI. -The class EEXI Technical File is approved. -A shaft power limitation (ShaPoLi) brought us into compliance.

Flag State

The country in which a ship is registered; it exercises regulatory jurisdiction and oversight over the vessel’s safety, environmental compliance, and crew conditions.

-Panama is the vessel’s flag state. -Flag will audit the ISM system next month. -We’re switching to a European flag for tax and crewing reasons.

Freeboard

The vertical distance from the waterline to the main deck line; a safety margin that limits loading and is governed by the International Load Line Convention.

-Loadline marks confirm the summer freeboard. -Reduced freeboard in heavy weather can be risky. -Freeboard calculations changed after the retrofit.

GM (Metacentric Height)

A primary indicator of a ship’s initial transverse stability; the distance between the center of gravity (G) and metacenter (M). Higher GM increases stiffness and roll acceleration; too low risks capsizing.

-GM is too high—she’s rolling uncomfortably fast. -Cargo stow changed GM; we’ll recalc stability. -Positive GM indicates initial stability but affects seakeeping.

Gross Tonnage (GT)

A dimensionless measure of a ship’s internal volume, calculated per an international formula; used for regulatory thresholds, fees, and some manning rules.

-Port dues are based on GT. -SOLAS applicability depends on GT thresholds. -GT rose after adding accommodation modules.

Heavy Fuel Oil (HFO)

A residual, high-viscosity marine fuel historically common on deep-sea ships; now often used with exhaust gas cleaning or replaced by low-sulfur fuels to meet emissions limits.

-We’ll keep burning HFO with a closed-loop scrubber. -VLSFO stability is better than the old HSFO cut. -Cold flow properties require heating HFO before injection.

Hull Form

The geometric shape of a vessel’s underwater and above-water body, driving hydrodynamic resistance, seakeeping, and fuel efficiency; optimized via towing-tank tests and CFD.

-The new bulbous bow reduces resistance at 14 knots. -CFD showed better energy efficiency with the modified hull form. -Shallow-draft hulls trade speed for access.

Ice Class

A structural and machinery rating (per IACS or national rules) that certifies a ship for operation in ice-infested waters with specified reinforcement and power.

-An Ice Class 1A hull is required for winter Baltic ops. -Propeller strengthening is part of the ice notation. -We adjusted insurance premiums for the higher ice class.

IMO (International Maritime Organization)

The United Nations agency that sets global maritime safety, security, and environmental standards via conventions, codes, and guidelines.

-IMO adopted CII and EEXI as part of its GHG strategy. -SOLAS and MARPOL are IMO conventions. -We monitor IMO MEPC outcomes for future compliance.

ISM Code

The International Safety Management Code requiring a safety management system (SMS) for the safe operation of ships and pollution prevention, audited for compliance.

-The DOC audit is due under ISM. -Report the near-miss per the ISM procedures. -The SMS manual was updated to reflect new hot-work controls.

ISPS Code

The International Ship and Port Facility Security Code establishing security measures to deter maritime terrorism and illicit acts through ship and port facility security plans, roles, and levels.

-The port raised the security level under ISPS. -We coordinated the Ship Security Plan with the CSO. -Access control drills are required by ISPS.

Jones Act

U.S. cabotage law requiring vessels moving goods between U.S. ports to be U.S.-built, U.S.-flagged, U.S.-owned, and largely U.S.-crewed.

-We need a Jones Act-compliant vessel for this U.S. coastwise move. -Charter party must affirm U.S.-built, owned, and crewed. -A foreign-flag feeder is not allowed under the Jones Act.

Keel Laying

A formal shipbuilding milestone marking the start of hull assembly; often triggers financing, insurance, and contractual events.

-Keel laying triggers milestone payment two. -Delivery schedule counts from keel laying date. -Class witnessed the keel laying ceremony.

Knot

A unit of vessel speed equal to one nautical mile per hour (1 kn ≈ 1.852 km/h).

-Service speed is 19 knots. -We’ll reduce to 12 knots for fuel savings. -Speed through water is 1–2 knots less than over ground due to current.

Laytime

The contractually allowed time for loading and/or discharging cargo under a voyage charter; if exceeded, demurrage is payable.

-Laytime starts at 0800 after valid NOR. -We exceeded laytime and incurred demurrage. -Interruptions for bad weather are laytime exceptions.

Length Overall (LOA)

The maximum length of the vessel’s hull measured parallel to the waterline from the extreme forward point to the extreme aft point; used for port, berth, and canal constraints.

-Berth can take up to 366 m LOA. -Tugs prefer a tug point closer to mid-LOA. -LOA limits determine canal booking category.

LNG Bunkering

The transfer of liquefied natural gas as marine fuel via truck, shore, or ship-to-ship operations, requiring specialized safety, training, and equipment under the IGF Code.

-Truck-to-ship LNG bunkering scheduled at 0200. -We’ll follow IGF Code procedures for LNG bunkering. -Dual-fuel engines require methane slip monitoring.

MARPOL Annex VI

The MARPOL air pollution annex covering SOx, NOx, particulate matter, ozone-depleting substances, VOCs, and fuel quality; establishes ECAs/SECAs and GHG measures.

-SECA limits sulfur to 0.10%. -We’re Tier III NOx compliant in ECAs. -Fuel changeover is logged for Annex VI compliance.

MLC (Maritime Labour Convention)

An ILO convention setting minimum standards for seafarers’ working and living conditions, including contracts, wages, hours of rest, medical care, and repatriation.

-The DMLC was updated after the crew welfare audit. -MLC sets minimum rest hours and accommodations. -PSC will check MLC certificates.

Mooring

The operation and equipment used to secure a vessel to a berth or buoy using lines, winches, and bollards; requires careful planning to manage loads and snap-back risk.

-Prepare a 4-2-2 mooring arrangement forward. -Snap-back zones must be marked on deck. -We’re installing shore tension monitoring to improve mooring safety.

Net Tonnage (NT)

A volumetric measure of a ship’s usable cargo-carrying spaces; used for certain fees and regulatory thresholds alongside gross tonnage.

-Canal tolls are assessed on NT. -NT changed after cargo space reconfiguration. -Certificate lists both GT and NT.

Notice of Readiness (NOR)

A formal notice by the master that the ship has arrived and is ready in all respects to load or discharge; starts the laytime clock per the charter party.

-Master tendered NOR at 0745 LT. -NOR was invalid due to berth being unavailable. -Laytime commenced six hours after valid NOR per charter.

Off-hire

A time charter term for periods when the vessel is unavailable for service and hire payments are suspended, subject to charter party clauses.

-Main engine failure placed the ship off-hire for 18 hours. -Off-hire periods reduce TCE earnings. -Charterer disputed off-hire for weather delay.

Offshore Support Vessel (OSV)

A broad category of ships (e.g., PSV, AHTS, SOV) that support offshore energy construction, production, maintenance, and logistics, often equipped with dynamic positioning.

-The PSV supports platform resupply. -DP2 is required for the walk-to-work SOV. -AHTS availability is tight in this basin.

P&I Club

A mutual insurer providing protection and indemnity coverage for shipowners and charterers against third-party liabilities, including pollution, collision, cargo, and crew claims.

-The owner’s P&I is with an IG Club. -P&I covers third-party liabilities like pollution and crew claims. -We notified P&I after the allision.

Panamax

A ship size category defined by Panama Canal dimensional limits; now commonly distinguished as ‘Panamax’ (original locks) and ‘New Panamax/Neopanamax’ (expanded locks).

-This bulker is ‘New Panamax’ compliant. -Panamax beam limits affect cargo intake. -Transit slots depend on Panamax booking category.

Port State Control (PSC)

Regulatory inspections by coastal states to verify foreign ships’ compliance with international safety, security, and environmental standards; serious deficiencies can lead to detention.

-PSC detained the vessel for ISM deficiencies. -We monitor Tokyo and Paris MoU performance lists. -Crew prepared for a PSC inspection on arrival.

Reefer

A refrigerated cargo unit or vessel designed to transport temperature-controlled goods; in containers, refers to the powered refrigerated boxes and their handling.

-We have 1,000 reefer plugs on deck. -Pre-trip inspection is required for reefer boxes. -Stow away from heat sources to protect reefer cargo.

Retrofit

The modification of an existing vessel with new equipment or design changes to improve compliance, efficiency, safety, or capability.

-We’ll retrofit a scrubber and EPL during the next dry dock. -Retrofit payback is under three years at current fuel spreads. -CFD supports the retrofit of a new bulbous bow.

Ro-Ro (Roll-on/Roll-off)

A ship type designed to carry wheeled cargo that is driven on and off via ramps; variants include Ro-Pax, ConRo, and PCC/PCTC car carriers.

-Ro-Ro decks require lashing plans for vehicles. -Ramp angle limits heavy cargo loads. -Ro-Pax combines Ro-Ro cargo with passenger service.

Scrubber (Exhaust Gas Cleaning System)

Equipment that removes SOx (and some particulates) from exhaust gas so ships can burn higher-sulfur fuels while meeting sulfur emission limits; can be open-loop, closed-loop, or hybrid.

-Open-loop scrubbers face port restrictions. -Washwater alkalinity must be monitored. -The scrubber OPEX is offset by cheaper HFO.

Sea Trial

Operational tests conducted at sea after construction or major refit to verify performance, safety systems, speed, maneuvering, and contractual requirements.

-Measured speed on sea trials met the contract. -We recorded noise and vibration levels during trials. -DP trials will follow builder’s trials.

SOLAS (Safety of Life at Sea)

The primary international convention setting minimum safety standards for the construction, equipment, and operation of ships.

-Bridge firefighting gear requirements come from SOLAS. -Lifeboat drills are mandated by SOLAS. -We updated LSA per the latest SOLAS amendments.

TEU (Twenty-foot Equivalent Unit)

A standardized measure of containerized cargo capacity equivalent to one 20-foot container; used for ship capacity, throughput, and trade statistics.

-The ship’s nominal capacity is 14,000 TEU. -Slot utilization exceeded 95% TEU. -Reefer TEU require more power allocation.

Time Charter

A hire arrangement where the charterer pays a daily rate to use the vessel for a period, providing bunkers and directing voyages, while the owner operates and maintains the ship.

-The vessel fixed on time charter at $28,000/day. -Off-hire clauses were heavily negotiated. -Charterer controls employment; owner manages the ship.

Trim

The difference between a ship’s forward and aft drafts; affects resistance, propulsion efficiency, and clearance and is actively optimized for fuel savings.

-Trim by the stern improved propeller immersion. -We used a trim table to cut fuel burn. -Draft marks show excessive trim at light ballast.

Under Keel Clearance (UKC)

The vertical distance between the ship’s keel and the seabed; managed to avoid grounding, considering tides, squat, heave, and bathymetry.

-Pilot requires 10% UKC in the channel. -Squat at 12 kn reduces UKC significantly. -We use dynamic UKC calculations based on tide and wave.

VDR (Voyage Data Recorder)

A ‘black box’ for ships that records navigational and operational data (e.g., position, audio, radar, alarms) to aid incident investigation and safety improvements.

-VDR data was pulled after the incident. -Annual VDR performance test is due. -Bridge audio and radar images are stored by the VDR.

Voyage Charter

A contract to carry a specific cargo between named ports for a freight rate, with agreed laytime/demurrage terms; owner pays voyage costs like bunkers and port charges.

-We fixed a voyage charter with laycan 1–5 Oct. -Demurrage applies if loading exceeds laytime. -Freight rate agreed per metric ton under voyage charter.

Wind-Assist Propulsion

Technologies such as rotorsails, wing sails, kites, or suction sails that harness wind to reduce main engine load and fuel consumption.

-Installing two Flettner rotors cut fuel by ~8%. -We’re trialing suction wings on the bulk carrier. -Routing was updated to leverage wind-assist gains.

Z-Drive (Azimuth Thruster)

A steerable propulsion unit that rotates 360 degrees to direct thrust without a conventional rudder; common on tugs, ferries, and DP vessels.

-The tug’s Z-drives give exceptional maneuverability. -We’ll inspect the azimuth seals during dry dock. -DP capability improves with azimuthing thrusters.