Ship-to-Ship Relays Are Moving Cargo Across the Strait of Hormuz in Two Stages

At a Glance

• One product tanker recorded 15 distinct meeting partners across two anchorage clusters in 90 days, with four transfers confirmed by cargo model.
• The structure is a relay, with cargo picked up inside the Gulf and handed onward outside it, so no single vessel carries the parcel end to end.
• The largest meeting in the record, with a Russia-sanctioned crude tanker, is the one where cargo movement is inferred rather than confirmed.
• A second products tanker works the identical two anchorages and shares counterparts, indicating a network rather than two independent operators.
• Some counterparts carry an Iran-program risk flag that appears to derive from the meeting itself rather than from independent evidence.

One Tanker Met Fifteen Counterparts in Ninety Days

Between May 27 and August 27, 2026, Windward tracked a Barbados-flagged product tanker of roughly 40,000 deadweight tonnes across two anchorage clusters at opposite ends of the Strait of Hormuz.

Inside the Gulf, it worked the Basrah and Kuwait anchorages. Outside, it worked Fujairah and Shinas. Across the window, it recorded 15 distinct meeting partners, more than any other vessel in the reviewed set, and four transfers corroborated by cargo model.

The vessel is not the endpoint of any of these movements. It is the middle.

The Relay Splits One Cargo Movement Into Two Legs

The pattern is consistent enough to describe as a structure.

Feeder and port tankers hand cargo to the intermediary at the Basrah and Kuwait anchorage, inside the Gulf. The intermediary then transits the strait and hands that cargo onward to different tankers waiting at Fujairah and Shinas, on the Gulf of Oman side.

Neither leg is unusual on its own. Ship-to-ship transfer at anchorage is routine commercial practice across both clusters. What the 90-day view shows is the same vessel performing both roles repeatedly, receiving inside and delivering outside, rather than carrying a cargo on its own bill of lading from load port to discharge port.

For a counterparty screening a fixture, that structure matters. The vessel named on the documentation for either leg is real, and its behavior is unremarkable. The movement of the cargo across the chokepoint sits in the gap between the two.

Two Transfers Are Confirmed at Parcel Level

The distinction between what is confirmed and what is inferred carries the whole analysis, so it is worth stating plainly which is which.

Two legs are corroborated directly.

A load at Basrah ship-to-ship between August 5 and 6, recorded by cargo model at approximately 34,547 units, with Vortexa’s cargo timeline tying the same transfer to a 48,998-barrel fuel oil parcel loaded at Khor Al Zubair, Iraq, on July 9 and discharged on August 14. That parcel accounts for the vessel’s most recent draft change and destination switch.

A discharge at Shinas on July 22 to a second tanker, also cargo-model corroborated by IMO match.

Everything else in the record is a meeting. Position, duration, and vessel geometry are established. Cargo movement is not.

The Largest Meeting Is the Least Confirmed

On August 14 and 15, the intermediary held a position alongside a 244-meter, 115,577 deadweight tonne crude tanker at Fujairah for close to 38 hours. The counterpart is Libyan-operated and has been on the Russia sanctions program since May 30, 2026. It is more than twice the intermediary’s deadweight.

By duration and by tonnage, this is the largest single event in the 90-day record. It is also the one with the least evidentiary support. Vortexa data has a gap across the meeting window, so cargo movement is inferred from timing and vessel geometry rather than confirmed at parcel level.

What is established sits on either side of it. The crude tanker had loaded roughly 109,800 tonnes at Yanbu on July 15 and 16. It then ran dark for approximately 90 hours crossing the Arabian Sea between July 22 and 26. After the Fujairah meeting, it made a verified discharge of 32,622 tonnes at Sohar on August 18 and 19.

A loaded arrival, a 38-hour alongside period, and a smaller verified discharge four days later is a sequence consistent with a transfer. It is not proof of one. Windward assesses the meeting as potentially the largest cargo event in the record while flagging that the parcel-level confirmation does not exist.

A Second Tanker Works the Same Two Anchorages

The intermediary does not appear to operate alone.

A second product tanker works the identical anchorage pair, Basrah and Kuwait inside the Gulf, Fujairah and Shinas outside it. The two share multiple counterparts, including the feeder tanker behind the confirmed August load and at least two service vessels, plus one tender that remains unresolved in the record.

Shared anchorages alone would prove little. Shared counterparts across both ends of the same route indicate a products-aggregation network rather than two vessels independently arriving at the same commercial logic.

Risk Flags Can Propagate Through the Meetings Themselves

Both product tankers carry an Iran-program risk flag, and several of their service-vessel counterparts carry the same flag.

That requires a caveat rather than an amplification. In some of these cases, the designation appears to be meeting-driven, meaning it derives from contact with a flagged vessel rather than from independent evidence of Iran-linked trade. Read uncritically, a network like this can appear to confirm itself, with each flagged meeting raising the risk profile of the next counterpart.

Anyone using this kind of data for a compliance decision needs to know which flags rest on independent evidence and which rest on association. Treating the second category as equivalent to the first produces false positives, and false positives are what erode confidence in screening.

As of the end of the review window, the intermediary had transited back into the Gulf and was positioned at the Kuwaiti tanker waiting area.

What This Changes for Counterparty Screening

Three implications follow for anyone vetting a fixture, underwriting a voyage, or financing a cargo through this corridor.

Screen the movement as well as the vessel. Vetting the named carrier is necessary, and it stays necessary. What a relay structure adds is that a clean result on the vessel does not describe the full movement, because the tanker on the paperwork for one leg is not the one that carried the cargo across the chokepoint. The counterparties on either side of the transfer are part of the picture the fixture does not name.

Treat repeated anchorage pairing as an indicator. A single ship-to-ship at Fujairah is routine. The same vessel receiving at one anchorage cluster and delivering at another, repeatedly, across a 90-day window, is a pattern that only becomes visible with meeting history at vessel level.

Separate confirmed from inferred before acting. Four transfers in this record are corroborated by cargo model. Eleven meetings are not. Both categories are useful, and they support different decisions. Confirmed transfers support a compliance finding. Inferred meetings support further investigation.

The Chokepoint Is Being Crossed in Segments

Nothing in this record is a confirmed sanctions violation, and none of it should be described as one.

What it does show is that cargo is moving across the Strait of Hormuz through an intermediary structure that no single bill of lading describes in full. The vessel that loads inside the Gulf is not the vessel that delivers outside it, and the entity that clears due diligence on either leg is not the one whose behavior connects them.

That structure is legible only across a full meeting history, and only when the distinction between what the data confirms and what it suggests is preserved rather than collapsed.

Meeting History Is What Makes a Relay Visible

None of this resolves from a position report. A single ship-to-ship at Fujairah tells you nothing, and neither does a single clean vessel screen.

Windward finds structures like this by holding the full behavioral record for every vessel and every meeting, then reading them together. Who a vessel met, where, for how long, how often the same pairing recurs, and which of those contacts a cargo timeline can account for. A relay only becomes visible when the same hull is seen receiving inside the Gulf and delivering outside it, again and again, with the counterparties on both ends resolved to real identities.

That is also what keeps the finding honest. The same record that surfaces the pattern is what shows four transfers standing up to parcel-level checking and eleven not, which is the difference between a compliance finding and a lead worth investigating.