Ship-to-Ship TransferSTS
Transferring cargo directly between two vessels moored alongside, often at anchor or offshore rather than at a terminal.
A ship-to-ship (STS) transfer moves cargo — typically crude, products, LNG or LPG — from one vessel to another lying alongside, using fenders and hoses, instead of going through a shore terminal. It is used for lightering large tankers into smaller ones, for offshore loading, and to consolidate or break bulk parcels.
STS is a legitimate, routine operation, but it is also a recurring tactic for obscuring the origin of sanctioned or "dark-fleet" cargoes, especially when paired with AIS gaps, so STS activity is closely watched in compliance screening.
On The Maritime
Also known as: STS, ship to ship transfer, lightering.
Related terms
Dark Fleet
Ageing, opaquely owned and often uninsured tankers that move sanctioned oil while disguising their movements.
Automatic Identification SystemAIS
A VHF transponder system that broadcasts a ship’s identity, position, course and speed for collision avoidance and tracking.
Sanctions
Government measures restricting trade or dealings with designated entities, vessels, cargoes or jurisdictions.
Bill of LadingB/L
The document that acts as receipt for cargo, evidence of the contract of carriage, and (when negotiable) document of title.
Plain-English reference definition — our own explanation of a standard shipping concept, not a licensed source or legal advice. See the full glossary or the broader maritime dictionary.
Last reviewed: June 2026.