The Cocaine Is Below the Waterline and the Crew Has No Idea

At a Glance

• Windward MIOC has documented 20 confirmed sea chest contamination cases across four continents since 2017, with cumulative seizures above 2 tonnes.
• The method is simple. A dive team places sealed packages inside a vessel’s sea chest at the origin port. A second team (or even the same team) retrieves them at the destination. The ship sails the route it was always going to sail.
• Crews are consistently assessed as unwitting. The exposure sits in a shore-based diver-broker network that never touches anyone on board.
• Bulk carriers and chemical/oil tankers carry the highest exposure. Long port calls and predictable loading windows give divers time to work.
• Nearly every detection to date has been intelligence-led. Most ports have no underwater forensic or ROV capacity at scale, so routine hull inspection almost never finds anything.

A Concealment Method That Doesn’t Need the Ship’s Cooperation

Windward MIOC has documented 20 confirmed cases of narcotics concealed inside vessel sea chests since 2017, linking Latin American origin ports to destinations in Europe, Asia-Pacific, Oceania, and North America. Cumulative seizures across those cases exceed 2 tonnes. At least one case involved specialized stealth diving equipment.

The sea chest is a recessed cavity in the hull, below the waterline, that draws in seawater for cooling and ballast. It’s covered by a grating and accessible only to a diver. Nothing about it appears on a cargo manifest, a container seal record, or a crew list.

That makes it close to ideal for a trafficking network. The load never enters the cargo. It never passes a terminal scanner. Nobody on board loads it, sees it, or knows it’s there. The vessel is infrastructure the network borrows for one voyage and hands back.

On Sunday, May 10, 2026, Brazilian Federal Police and Navy divers pulled a dozen bundles from the sea chest of the bulk carrier Green K-Max 1 at the Port of Santos, recovering 341 kg of cocaine. The Federal Police said they were acting on intelligence work and risk monitoring carried out at the Port of Santos. 

The Green-K Max 1 had arrived at the port from India and was reported to be loading and preparing to depart for Poland. The 80,856 dwt vessel built in 2019 is registered in Liberia and managed by Greece’s Aegean Eco Carriers. The load went in before the ship left the origin port, was found by an intelligence-driven dive rather than a routine inspection, and the crew was not implicated. Every element of the method in one case.

Why the Risk Moved Below the Waterline

The pattern across MIOC’s August counter-narcotics work is consistent: enforcement pressure displaces trafficking rather than eliminating it. Sea chest contamination is the clearest example.

Container terminal screening has improved. Rip-on/rip-off operations that depend on port insiders are harder to run and easier to prosecute. So the risk moved to the one part of the ship nobody inspects on a normal port call.

What has grown in its place is a shore-based diver-broker network, and MIOC assesses it as increasingly professionalized. Brokers recruit divers, select vessels, and coordinate the retrieval dive at the destination. The stealth diving equipment documented in at least one case points to operators who have invested in the method and intend to keep using it.

Which Vessels Carry the Exposure

Bulk carriers and chemical/oil tankers sit at the top of the exposure profile, and the reason is time.

A bulk carrier alongside for a multi-day loading window, or at anchor waiting for a berth, gives a dive team hours of predictable access in low-visibility water at a port with limited underwater monitoring. Container vessels, with faster turnarounds and busier terminals, offer far less.

Route pairing matters as much as vessel type. The confirmed cases share a pattern: a Latin American origin port, a long ocean transit, and a destination market where the retrieval network already operates. A vessel that runs that pairing repeatedly, with extended dwell at origin, carries a materially different risk profile from one that doesn’t, even if the ownership, crew, and cargo are identical.

Why Hull Inspections Don’t Catch It

Detection in the confirmed cases has been almost entirely intelligence-led. A tip, an investigation into the broker network, a retrieval dive interrupted at the destination. Routine inspection has rarely been the trigger.

The reason is capacity. Most ports worldwide lack underwater forensic or ROV capability at scale. Diver inspections are slow, expensive, and reserved for vessels already flagged. A hull that clears a standard port state control inspection has told you nothing about its sea chest.

For anyone assessing risk, that changes the meaning of a clean inspection record. Absence of a finding is not evidence of a clean hull. It is evidence that nobody looked below the waterline.

What This Means for Owners, Charterers, and Insurers

The immediate cost of a sea chest seizure lands on the vessel, not the network. Detention while authorities investigate, crew interviews, schedule loss, and a vessel name attached to a narcotics seizure in the public record. The network loses a load it priced as expendable. The owner loses weeks.

The instinct is to treat this as a crew-vetting problem. It isn’t. MIOC assesses crews as unwitting across the confirmed cases. Vetting the crew harder produces no signal because the crew has no involvement.

The exposure is in the vessel’s operating pattern: which origin ports it calls, how long it dwells there, which destination markets it pairs with, and whether that pairing matches the corridors where confirmed cases cluster. That is a pre-fixture and portfolio question, and it can be answered before the vessel sails.

What This Means for Enforcement

For port authorities and customs agencies, the constraint is the same one that makes the method work: too many hulls, too few divers.

Intelligence-led detection only scales if the list of vessels worth putting a dive team under is short and defensible before arrival. That requires vessel-level risk profiling built on port-call sequence, dwell behavior, route pairing against confirmed corridors, and ownership context, assembled ahead of the port call rather than after a tip arrives.

What to Watch

Three developments would indicate the method is spreading, and MIOC assesses all three as plausible over the next 12 months.

Retrieval failures are the first. Packages discovered by commercial divers during routine hull cleaning, rather than by law enforcement, would suggest volume has outgrown the retrieval network’s ability to service every load.

Origin diversification is the second. The confirmed cases cluster on Latin American origins. Evidence of the same method on West African or Southeast Asian export routes would confirm the playbook has been sold on.

The third is a shift toward smaller vessel classes. If bulk and tanker operators tighten dwell-time controls and underwater monitoring at high-risk berths, the method will follow the same displacement logic that created it and move to whichever hull type is inspected least.

Analysis by Manuel M.B. Assis Teixeira, Counter Narcotics Maritime Intelligence Analyst, Windward MIOC