Spain confronts the submerged threat posed by Russia’s ghost fleet

In December 2024, the Eagle S., an oil tanker flying the Cook Islands flag that had sailed from a Russian port, was detained by Finnish police. It was accused of damaging an electric cable and four other data cables on the floor of the Baltic Sea with its anchor. It may have been an accident, but repeated incidents prompted NATO the following month to launch a military operation, Baltic Sentry, deploying surveillance aircraft, ships, and drones to confront the undersea threat. Suspicions pointed to the so‑called Russian ghost fleet, with which the Putin regime is evading EU sanctions imposed after the invasion of Ukraine.

The latest annual report from the Department of National Security, under the Office of the Spanish prime minister, identifies sabotage of submarine cables and pipes (which carry electricity, data, and gas) as one of the “main concerns regarding hybrid threats” — those that occur in the gray zone where the line between peacetime and war is blurred. There is no record that Spain has so far suffered any deliberate attack on its undersea infrastructure, but COVAM (the Spanish Navy Maritime Surveillance and Action Operations Center), based in Cartagena, identifies some 50 ghost fleet vessels each week near Spanish waters (out of nearly 600 listed by the EU). Their presence in waters off the Canary Islands has increased five-fold in just one year, the report warns.

In its Mediterranean sector alone, Spain has 37 submarine cables, with a data transfer capacity of 811 terabits (billions of bits) per second, not including those that connect Europe with the Americas and Africa, or those that link the peninsula with the Spanish archipelagos, and those islands to each other. Spain is a communications hub between both sides of the Atlantic. Protecting hundreds of thousands of miles of undersea pipelines is a huge task that increasingly demands more military resources.

Its mission is to carry out patrols of “presence, surveillance, and deterrence” in the Exclusive Economic Zone — up to 200 miles from the coast — and in waters of national interest, according to Captain José María Liarte, head of the Navy Diving Center (CBA). When a vessel is detected conducting suspicious activity, the Navy identifies and questions it. If it does not leave the area, it may be seized and escorted to port, although that requires a court order. The ghost fleet vessels are not only a threat to submerged infrastructure but also to the marine ecosystem, since many are in poor condition and engage in dangerous activities such as transferring crude oil at sea. These ships are not the only ones the Navy monitors. It also tracks treasure hunters who plunder the underwater heritage formed by the wrecks of old galleons. To protect all this submerged wealth, the Navy has a diving unit with specialists in special operations, rescue, and explosive ordnance disposal. Their diving limit is about 100 meters, and beyond that depth submersible vehicles come into play.

Commander Javier Molina commands the 1st Minesweeper Squadron — in practice Spain’s only one — consisting of six vessels built with glass fiber‑reinforced plastic hulls to reduce their magnetic signature, each named after a river: Turia, Segura, Tambre, Sella, Tajo and Duero. This Tuesday the lead ship was sweeping the seabed off Málaga. When it encountered an unknown object, the ship first detected it and then classified it with its precision sonar.

To identify it, the ship deployed Pluto Plus, a roughly two‑meter‑long tethered vehicle that can descend to 300 meters to inspect the underwater environment. On a screen on the bridge, the Turia’s commanding officer, Lieutenant Commander Jesús Remírez Esparza, could watch live images from Pluto Plus’s camera. If destruction had been required, an 80‑kilogram explosive charge activated by remote control would have been placed on the suspicious object. For moored mines, the MiniSniper is reserved — a kamikaze drone that operates like a small, guided torpedo.

The frigate commander says the four Spanish minesweepers, despite being almost three decades old, are equal to those of other countries. The proof is that one of them will take rotational command of NATO’s mine‑countermeasure fleet in the first half of next year. They would also be tasked with clearing the Strait of Hormuz if that mission is launched, once a ceasefire is reached between Washington and Tehran and assuming Spain decides to participate. When asked how long the fleet would need to clear Hormuz, Molina replies with another question: “Tell me how many assets and how much time you can give me, and I’ll tell you what guarantees I can give that it will be clear.” Naval mine clearance is a meticulous, patient task that requires scanning the seabed and detecting sometimes imperceptible changes — something that today is reserved for expert eyes and that tomorrow could be aided by artificial intelligence. The mine is such a cheap weapon that it often does not even need to be placed; sometimes the mere threat is enough to disrupt all maritime traffic.

The Spanish Navy’s capabilities to protect the seabed will multiply next year when the Poseidón enters service, a 5,000‑ton, 91‑meter maritime action ship for underwater intervention equipped with an ROV (remotely operated vehicle) capable of operating at 6,000 meters. The Poseidón was originally conceived as a rescue ship for the S‑80 submarine and was intended to enter service alongside the new submersible vessel, which has not yet been possible. Its features will, however, allow it to carry out other tasks, such as inspecting the wreckage of the Ursa Major, the Russian ship mysteriously sunk in December 2024 some 60 miles from Cartagena. While the Poseidón is still pending, the Navy will this year receive the Proserpina, a smaller vessel, 32.9 meters long, with side‑scan sonar and an ROV for explorations up to 900 meters below the surface. To justify this deployment of assets, a veteran sailor explains that the undersea domain has already become the setting for a clandestine, silent war. It is wise to keep eyes and ears well attuned under the water to avoid surprises.

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