Insights · Compliance · Shadow fleet
A parallel fleet of ageing, anonymously owned tankers now moves the oil that mainstream shipping will not touch. It hides in plain sight by switching off its transponders and trading hands at sea — and learning to read the signals is the first line of defence.
"Shadow fleet" and "dark fleet" describe the same thing: the loosely defined collection of mostly oil tankers that carry sanctioned or price-capped cargo while operating outside the rules and services that govern the regulated market. These vessels do not use recognised Western insurers, frequently change name and flag, and routinely manipulate the signals by which the rest of the world tracks them. The fleet has no single owner and no membership list — it is identified by behaviour, not by registration.
Estimates of its size vary, but analysts and governments now count well over a thousand tankers in this category, a figure that has climbed steeply since 2022. What unites them is a willingness to move barrels that the mainstream tanker market has priced itself out of.
The catalyst was the oil price cap introduced by the G7 and the European Union in December 2022. The mechanism is indirect: rather than banning Russian crude outright, it forbids Western shipping, insurance and financial firms from servicing cargoes sold above a set ceiling — roughly $60 a barrel for Russian crude. The intent was to keep oil flowing while squeezing the revenue.
The unintended consequence was a parallel market. Operators willing to carry oil priced above the cap simply stopped using Western insurance and brokers, and a fleet of older tankers — bought up cheaply, often near the end of their service lives — emerged to serve it. Iranian and Venezuelan crude, already under longer-standing sanctions, moves through the same shadow logistics.
The fleet has a recognisable profile. Ships tend to share several of the following traits:
"Dark activity" is the operational signature of the fleet. The Automatic Identification System (AIS) is meant to broadcast a ship's identity and position continuously for safety; a shadow vessel treats it as something to be turned off, or falsified, when it would reveal too much. A tanker may go dark as it approaches a sanctioned loading terminal, reappearing hours later in open water with a full cargo and no record of where it came from.
The companion technique is the ship-to-ship (STS) transfer — pumping cargo from one tanker to another at sea, often in international waters away from any port. An STS transfer launders the cargo's paper trail: oil that loaded at a sanctioned terminal arrives at its destination on a different vessel, blended and re-documented, with the origin obscured. When both vessels go dark around the rendezvous, the transfer leaves almost no visible footprint.
A tanker that vanishes from the map for three days near a sanctioned port and reappears riding low in the water has told you everything except the truth. On reading AIS gaps in shadow-fleet operations
The risk is twofold. First, safety and the environment: an ageing, under-insured tanker carrying a million barrels through a busy strait is a casualty waiting to happen, and if it spills there may be no meaningful insurer to fund the clean-up. Second, sanctions exposure: anyone who charters, finances, insures or receives cargo from a shadow vessel risks breaching the very measures the fleet exists to evade.
No single signal is conclusive, but a cluster of them is telling. Watch for AIS gaps and position spoofing, identity or MMSI manipulation, ship-to-ship transfers in open water, dark calls at sanctioned ports, and a suspicious flag history of rapid reflagging. Cross-referencing these patterns against the vessel's ownership and sanctions standing is the practical defence — and it is exactly the work an open registry is built for.
You can start from the behaviour: watch a vessel's track on the live map, then open its file to check the compliance screening. Because Marifest keys every record to the permanent IMO number and screens 97,000+ vessels against OFAC, EU, UN and UK lists, a ship that reflags or renames to escape attention still ties straight back to its history. To understand the techniques in depth, read how AIS ship tracking works, why flag states enable reflagging, and how beneficial ownership is layered to hide who profits.
How Marifest helps
Marifest anchors every vessel to its permanent IMO number, so the tricks the shadow fleet relies on — renaming, reflagging, going dark — leave a trail you can follow on one record instead of losing it.
The live map shows a vessel's recent AIS track, so a sudden disappearance near a sanctioned loading region is visible rather than invisible.
Each file is keyed to the IMO number, so a fresh name or a new flag of convenience reconnects to the old record instead of resetting it.
Marifest matches 97,000+ vessels against the OFAC, EU, UN and UK sanctions lists, flagging a designated ship or owner on the vessel file.
The ownership chain links the single-ship company to its manager, operator and ultimate beneficial owner, so a clean hull with a dirty parent is exposed.