Ship-to-ship transfers: how a cargo loses its origin

The ordinary operation

Two ships come alongside in sheltered water. Fenders go out, hoses are connected, and cargo is pumped from one to the other. It happens thousands of times a year for entirely mundane reasons.

Big tankers cannot enter shallow ports, so they lighter part of their cargo into smaller vessels offshore. Traders consolidate several small parcels into one large one for a long voyage, or split a large one for several buyers. Floating storage needs periodic movement. None of this is exotic and none of it is unlawful.

MARPOL and the associated regulations govern how oil transfers between ships must be conducted and reported for pollution-prevention purposes, which tells you how normal the operation is: it has its own safety rulebook.

The same operation, used differently

Now consider what a transfer does to the paperwork.

A cargo loaded at a sanctioned origin has documents that say so: a bill of lading, a certificate of origin, cargo surveys. After a transfer at sea, the receiving vessel can issue a fresh set of documents describing a cargo loaded, in effect, from a ship rather than from a country. If the cargo is also blended with oil of another origin, the resulting parcel is genuinely a mixture, and describing its origin becomes a matter of choice.

That is the whole mechanism. Not smuggling in the cinematic sense: a documentary operation conducted in international waters, using an ordinary commercial procedure.

The legal position is unchanged by any of it. Sanctions attach to the origin of the goods and to the persons dealing in them. What the transfer changes is how hard it is for a buyer, an insurer or a bank three steps down the chain to know what they are handling.

Why the same few places

Transfer areas are chosen for physical and jurisdictional reasons at once.

The water must be sheltered enough for two large hulls to lie alongside safely, and deep enough for laden tankers. The location should be near the route the cargo is taking, because every extra mile costs money. And it helps if no coastal state has both the interest and the capacity to look closely.

Those constraints produce a short list of well-known anchorages, off Malaysia, in parts of the Mediterranean, in the Gulf of Oman and the Yellow Sea. Anyone who watches the trade knows where they are, which is itself a clue that this is not really concealment: it is jurisdictional arbitrage conducted in public.

What an authority actually looks at

The published advisories are consistent about the indicators.

An unreported transfer, where the operation was not notified as the rules require. A transfer conducted at night or with transponders off on one or both vessels. A transfer between a designated vessel and an undesignated one, which is the mechanism by which a cargo escapes its history. A transfer in an area with no commercial reason for the vessel to be there. And any transfer followed by documents that do not fit the voyage.

The United Nations reporting on North Korea sanctions has documented this pattern in detail for years, and the price-cap advisories describe the same behaviour in the Russian trade.

Where it shows up in the data

It mostly does not, and that is worth saying plainly. Sanctions lists record designations, not operations. You will not find “conducted a transfer at sea on this date” in the OFAC, UK or EU data.

What you will find is the trace it leaves in the reasons authorities publish. The EU’s Annex XLII grounds cite vessels that transport Russian oil “while practising irregular and high-risk shipping practices as set out in” the IMO resolution, which is a formulation that covers unreported transfers and transponder manipulation together. UK statements of reasons describe carrying oil of Russian origin to third countries.

So the honest way to use this site alongside a transfer story is: the listing tells you an authority reached a conclusion about the hull; the transfer evidence has to come from elsewhere, and needs the corroboration described in AIS: going dark and spoofing.

The safety problem underneath

Two laden tankers, some of them decades old, coming alongside in open water, without the safety management a port would impose, is a serious pollution risk. If something goes wrong, the response depends on insurance that may not pay and a flag state that may not answer.

That is why the IMO’s shadow-fleet resolution puts unreported transfers alongside fraudulent registration rather than treating them purely as a sanctions matter. The sanctions argument is contested between states. The argument that nobody wants a collision and a spill in their exclusive economic zone is not.