Ukraine strikes major blow to Russia’s Black Sea Fleet with underwater drone attack

Ukraine has dealt one of its most significant maritime blows of the war, strikes on Russian submarine with an unmanned underwater vehicle in what Kyiv says is the first successful attack of its kind.

On 15 December, special forces from Ukraine’s Security Service, working alongside the navy, targeted an Improved Kilo class submarine while it was moored in the Russian port of Novorossiysk. The attack was carried out using a so called “Sub Sea Baby” kamikaze drone, which Ukrainian officials say hit the £300m vessel and the jetty beside it.

Russia has denied that the submarine suffered serious damage. However, footage released following the explosion suggests otherwise. While a full assessment is still pending, military analysts say disabling a high value submarine alongside its berth represents a significant success for Ukraine.

The strike also underlines a wider trend. After being pushed out of its main base at Sevastopol in occupied Crimea, Russia’s Black Sea Fleet moved much of its force to Novorossiysk in search of safety. That refuge now appears increasingly vulnerable. While Russian ground forces continue to make slow gains on land, at sea the picture looks very different, with the Black Sea Fleet steadily retreating.

A serious loss for Russia

Beyond the symbolism, the loss of a single submarine matters. Russia has now lost two of its Kalibr cruise missile capable submarines, leaving perhaps only three in service with the Black Sea Fleet. These boats have been central to long range missile strikes on Ukrainian cities.

Their reduced numbers weaken Russia’s ability to launch sea based attacks and limit its capacity to threaten commercial shipping without detection.

Drones are often credited with transforming modern warfare, particularly on land. At sea, however, aerial drones have so far proved little more than slow and vulnerable missiles, as seen repeatedly in the Red Sea.

What has changed in the Black Sea is the effective use of surface and now subsurface drones against Russian vessels, many of which were stationary, anchored, or tied up in port. That greatly reduces the difficulty of the attack. The confined geography of the Black Sea also means Russian bases and anchorages are under constant threat, not just ships at sea.

Ukraine, by contrast, operates no major surface warships, giving Russia far fewer high value targets in return.

How the attack may have worked

Surface drones used by Ukraine are, in essence, fast suicide boats without crews. Similar threats have existed for decades and can be countered by alert and well trained warships operating at sea. Russia’s losses in this area reflect defensive shortcomings as much as Ukrainian innovation.

Penetrating a defended harbour underwater without a crew is far more complex.

How the Sub Sea Baby reached Novorossiysk remains unclear. It may have travelled on the surface or semi submerged over long distances, similar to drug smuggling vessels. Another possibility is deployment from a mothership, potentially even a civilian looking vessel.

Once close to the harbour, the drone would likely have submerged fully. At that point, maintaining communication becomes extremely difficult. One option would be a trailing cable linking it to a controller or to a communications buoy outside the harbour. Without that, the drone would have needed to operate autonomously.

Navigation underwater presents another challenge. Satellite systems such as GPS do not work beneath the surface. Inertial navigation is one option, though accuracy can be limited in small systems. Doppler navigation sonar, which tracks movement over the seabed, is another possibility and is already used by divers and some small underwater vehicles.

Active imaging sonar could also have been used to locate the submarine, but that would increase the risk of detection by Russian sensors and is more prone to error, especially without human control.

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However it was done, defence analysts say the operation represents a major technological achievement and one that Western militaries will be keen to understand and replicate.

Can ports be defended against this threat?

Defending against underwater drones is difficult. Traditional measures such as anti submarine nets and booms can help but are slow to install and not foolproof. A drone could simply wait until an opening appears.

Modern short range sonar systems can detect approaching divers or drones, but detection alone is not enough. A vehicle carrying a large explosive charge needs to be stopped well outside the harbour.

The most effective defence may still be to keep warships at sea. An underwater drone like the Sub Sea Baby is unlikely to match the speed and pursuit capability of a modern torpedo, at least for now.

Four years into the war, Russia’s failure to adapt to Ukrainian innovation continues to surprise observers. Basic defensive measures appear lacking, particularly around key naval infrastructure.

That vulnerability is not unique to Russia. Western ports and energy facilities face similar risks. A comparable attack could, in theory, target a British naval base or critical infrastructure such as gas terminals, using covert platforms ranging from disguised civilian vessels to specialised submarines.

With limited underwater surveillance assets and attack submarines often confined to port, detection would be challenging.

As peace talks continue, Ukraine has shown it is still innovating rapidly in the use of uncrewed systems. In an era of tight defence budgets, military planners across Europe and beyond are likely to study this attack closely. Russia has once again failed to defend against a new form of warfare, and many experts warn others may be no better prepared.