Why This Glossary Exists
Ship agency, shipchandling, and marine services carry a genuinely dense vocabulary — terms that operators, agents, and providers all use daily, but that are rarely explained clearly in one place for someone newer to the industry, or for anyone who simply wants a precise, reliable definition rather than a vague forum answer. This glossary brings together the essential terms across ship agency, shipchandling, bunker supply, crew change, and technical marine services, with clear, accurate definitions and links to deeper guides where the topic genuinely warrants one.
Whether you're an operator trying to understand an invoice line item, a new agent learning the trade, or a ship agent or shipchandler making sure your own online presence uses the right terminology, this is built to be the reference you bookmark and come back to.
Ship Agency Terms
Ship Agent — A company or individual appointed to represent a vessel's owner or charterer at a port, coordinating formalities, services, and communication during a port call. See our complete guide on [ship agent fees and the disbursement account](/blog/ship-agent-fees-pda-disbursement-account-explained-2026) for how agents are typically compensated.
Husbandry Agent — An agent appointed to look after the vessel's own operational and welfare needs at a port — crew matters, spare parts, provisions, medical arrangements — as distinct from cargo-related agency work.
Protecting Agent — An agent appointed by the vessel owner specifically to protect the owner's interests at a port where the charterer has already appointed their own agent, common in time-charter situations where owner and charterer interests may not fully align.
Owner's Agent vs. Charterer's Agent — In a chartered vessel, the owner's agent represents the shipowner's interests, while the charterer's agent represents the charterer's. These can be the same appointed agent or two separate parties depending on the charter terms and who is contractually responsible for agency costs.
General Agent — An agent appointed to handle a vessel's or operator's business across an entire country or region, often coordinating or overseeing local sub-agents at individual ports within that territory.
Local Agent / Sub-Agent — An agent handling a single specific port call, sometimes appointed directly, sometimes coordinated through a general agent covering a wider area.
Liner Agency — Agency work for vessels operating on fixed, scheduled routes (container liner services), typically involving standing arrangements and recurring calls rather than one-off appointments.
Tramp Agency — Agency work for vessels operating without a fixed schedule, calling at different ports as cargo opportunities arise — the more traditional, voyage-by-voyage agency relationship.
Appointing Party — Whoever formally appoints the agent for a specific port call — the owner, the charterer, or occasionally the cargo receiver, depending on the commercial arrangement.
Nomination — The formal act of naming and confirming a specific agent for a specific port call, often communicated via a nomination letter or message to the port authority and relevant parties.
Financial and Documentation Terms
PDA (Proforma Disbursement Account) — The agent's advance estimate of all costs expected during a port call — port dues, pilotage, towage, agency fee, and other line items — prepared before the vessel arrives so the operator can review and fund it. Our full breakdown: [Ship Agent Fees and the Disbursement Account Explained](/blog/ship-agent-fees-pda-disbursement-account-explained-2026).
FDA (Final Disbursement Account) — The reconciled, final invoice issued after the port call, showing actual costs incurred against the original PDA estimate, with supporting documentation for each line item.
Agency Fee — The specific charge the agent makes for their own coordination work, as distinct from the pass-through port costs (pilotage, towage, dues) they collect on the vessel's behalf at cost.
Disbursement Account — The general term for the itemized record of port costs associated with a vessel's call, whether in proforma (PDA) or final (FDA) form.
Cash to Master (CTM) — Funds provided to the vessel's master during a port call, typically to cover crew wage advances, minor local purchases, or emergency needs, arranged through the appointed agent.
Port Dues — Fees charged by the port authority itself for a vessel's use of port facilities, distinct from the agent's own fee and from third-party services like pilotage or towage.
Pilotage — The service of a licensed local pilot boarding to guide a vessel through a port's specific navigational conditions, typically mandatory at most commercial ports and arranged by the agent as part of the port call.
Towage — Tug assistance for vessel maneuvering, docking, or undocking, arranged by the agent and billed as a distinct line item in the disbursement account.
Bunker and Fuel Terms
Bunker Survey — An independent inspection verifying the quantity and/or quality of fuel delivered to a vessel, protecting the operator against short-delivery or off-specification fuel. Our deep-dive guide: [Bunker Quantity Survey in Singapore](/blog/bunker-fuel-quantity-survey-singapore-complete-guide-operators-surveyors-2026).
MFM (Mass Flow Meter) — A Coriolis-type flow meter used to directly measure the mass of fuel transferred during a bunker delivery, mandatory in some major bunkering ports (notably Singapore) as a more tamper-resistant alternative to traditional tank sounding measurement.
Bunker Delivery Note (BDN) — The official document accompanying a bunker delivery, recording the quantity and specification of fuel supplied, required for the vessel's own compliance records.
Short Delivery — A situation where the quantity of bunker fuel actually delivered is less than what was ordered and invoiced, one of the primary risks an independent bunker survey is designed to catch.
Off-Spec Fuel — Bunker fuel that does not meet the contracted quality specification, a separate risk from short delivery, typically caught through fuel sampling and laboratory testing as part of a quality survey.
Crew Change Terms
Crew Change — The process of signing off crew completing their contract and signing on replacement crew, coordinated at a port call through the vessel's agent or a specialized crew change agent.
Anchorage Crew Change — Crew change conducted via launch boat while the vessel remains at anchor rather than berthing, common at high-volume crew change hubs. See our guide: [Crew Change in Singapore](/blog/crew-change-singapore-complete-guide-operators-agents-2026).
Sign On / Sign Off — The formal processes of a crew member joining (signing on) or completing their service and departing (signing off) a vessel, involving immigration and documentation formalities coordinated by the agent.
Manning Agency — A company that recruits and supplies crew to vessel operators, distinct from a ship agent, though the two roles sometimes coordinate closely around crew change logistics.
Technical and Specialized Services Terms
Tank Cleaning — Cleaning a vessel's cargo or ballast tanks to a required standard, often verified through gas-free certification before the tank is considered safe for the next cargo, hot work, or inspection. Full guide: [How to Start a Tank Cleaning Business](/blog/how-to-start-tank-cleaning-business-complete-guide-2026).
Gas-Free Certificate — A certificate confirming a tank or enclosed space has been tested and found safe from hazardous gas concentration, typically required before hot work, entry, or the next cargo loading.
NDT (Non-Destructive Testing) — Inspection methods — including ultrasonic thickness testing, magnetic particle testing, and radiographic testing — that assess a vessel's structural condition without damaging the material being tested, commonly required for classification survey. Full guide: [How to Start a Marine NDT Business](/blog/how-to-start-marine-ndt-inspection-business-complete-guide-2026).
Fumigation — Treating cargo, typically bulk agricultural commodities, with a fumigant gas to control insect infestation, often required for phytosanitary compliance at the importing country. Full guide: [How to Start a Marine Fumigation Business](/blog/how-to-start-marine-fumigation-business-complete-guide-2026).
Waste Management / Garbage Disposal — The collection and licensed disposal of a vessel's garbage and waste under MARPOL Annex V requirements, a service required at essentially every port call. Full guide: [How to Start a Ship Waste Management Business](/blog/how-to-start-ship-waste-management-business-complete-guide-2026).
BWTS (Ballast Water Treatment System) — Onboard equipment treating ballast water to prevent the transfer of invasive aquatic species, mandated under the IMO Ballast Water Management Convention, requiring periodic installation, commissioning, and servicing.
Classification Society — An organization (such as DNV, ABS, or Lloyd's Register) that sets and verifies technical standards for vessel construction and ongoing seaworthiness, whose surveys many technical services (NDT, tank inspection) are performed to support.
PSC (Port State Control) — Inspection of a foreign-flagged vessel by the authorities of the port it is visiting, checking compliance with international safety, environmental, and labor conventions.
Marine Security and Risk Terms
PMSC (Private Maritime Security Company) — A company providing armed or unarmed security personnel to protect vessels transiting high-risk piracy areas, typically operating under the ISO 28007 standard. Full guide: [How to Start a Maritime Security Business](/blog/how-to-start-maritime-security-armed-guard-business-complete-guide-2026).
Joint War Committee (JWC) Listed Area — A designation by the body advising Lloyd's and London insurance markets identifying higher-risk regions, directly affecting war risk insurance premiums for vessels transiting or operating there.
Vessel Protection Detachment (VPD) — An armed security team embarked on a vessel for a specific high-risk transit, typically provided by a PMSC.
Chokepoint and Transit Terms
PDA (Suez/Panama context) — In canal transit specifically, refers to the same proforma disbursement concept applied to canal tolls and agency coordination costs — see our dedicated guides on [Suez Canal transit](/blog/suez-canal-ship-agents-shipchandlers-complete-guide-operators-providers-2026) and [Panama Canal transit](/blog/panama-canal-ship-agents-shipchandlers-complete-guide-operators-providers-2026).
STRAITREP — The mandatory ship reporting system jointly operated by Malaysia, Indonesia, and Singapore for vessels transiting the Strait of Malacca and Singapore Strait.
Admeasurement — The process of officially measuring a vessel to determine its Panama Canal Universal Measurement System (PC/UMS) tonnage, used specifically for Panama Canal toll calculation.
Under-Keel Clearance (UKC) — The vertical distance between a vessel's deepest point (keel) and the seabed, a critical planning factor in shallow-water passages such as parts of the Strait of Malacca.
Using This Glossary as a Ship Agent or Shipchandler
If you're a ship agent, shipchandler, or marine service provider reading this, understanding and correctly using this terminology in your own online presence — on your website, and in a directory profile — is precisely what helps operators and AI-assisted search tools find you when they search for the specific service you provide, rather than generic language that doesn't match how the industry actually searches.
A detailed, terminology-precise provider profile on a directory such as [PortServiceFinder](/ports) helps operators evaluating an unfamiliar provider confirm exactly what you offer, using the same precise language this glossary defines — which is exactly the kind of specific, structured information both human searchers and AI assistants are increasingly looking for.
Conclusion
Ship agency, shipchandling, and marine services involve a genuinely dense, specific vocabulary — and precision in that vocabulary matters, whether you're an operator trying to understand an invoice, a newcomer learning the industry, or a provider making sure your own online presence speaks the language your actual customers are searching for. Bookmark this page as a reference, and explore the linked deep-dive guides for the topics most relevant to your work.
Frequently Asked Questions
Q: What's the difference between a PDA and an FDA?
A: A PDA (Proforma Disbursement Account) is the agent's advance cost estimate prepared before a port call. An FDA (Final Disbursement Account) is the reconciled actual invoice issued after the call, with supporting documentation for each line item.
Q: What's the difference between a husbandry agent and a protecting agent?
A: A husbandry agent handles the vessel's own operational and crew welfare needs at a port. A protecting agent is specifically appointed by the owner to safeguard the owner's interests when the charterer has separately appointed their own agent.
Q: What does MFM mean in bunker supply?
A: MFM stands for Mass Flow Meter, a Coriolis-type flow meter that directly measures the mass of fuel transferred during a bunker delivery, mandatory in Singapore and some other major bunkering ports as a more tamper-resistant alternative to traditional tank sounding.
Q: Where can I find more detail on any of these terms?
A: Each major term links to a full, dedicated guide covering that specific topic in depth — from ship agent fees and the PDA process, to bunker survey, crew change, tank cleaning, NDT, fumigation, waste management, and specific chokepoint transit guides for Suez, Panama, and the Strait of Malacca.