Analyst explains how Ukrainian underwater drone struck Russian Kilo-class submarine

Sutton, a well-known OSINT analyst and author of the Covert Shores blog specializing in naval warfare, submarines, and maritime drones, outlined his assessment in a detailed video analysis. He has previously examined multiple Ukrainian strikes against Russia’s Black Sea Fleet and assessed Russian naval capabilities.

This time, Sutton analyzed video footage released by Ukraine’s Security Service showing the strike on a Project 636.3 Varshavyanka-class submarine — known as the Kilo class in NATO terminology — in Novorossiysk.

According to Sutton, the attack appears to have caught Russian forces off guard. The entrance to the naval harbor remained open, and there were no visible signs of defensive fire or countermeasures, suggesting the Ukrainian drone was not detected.

However, to enter the harbor, the underwater drone would have had to approach the entrance from the opposite side and then execute a sharp, angled turn to reverse course and strike one of the Varshavyanka-class submarines moored at the base — likely one of three present at the time, Sutton said.

The analyst illustrated the drone’s probable route in his video analysis.

“In reality, any vessel — surface or underwater — would have to approach from the left side of the frame, pass various ships, barges, and other obstacles through the harbor entrance, and then turn sharply back inside the harbor toward the submarine,” Sutton said.

“That’s extremely challenging navigation — very impressive navigation,” he added.

Based on the footage, Sutton identified three Kilo-class submarines at the Novorossiysk base at the time of the strike. He believes the Sub Sea Baby drone hit the aft section of one submarine — the area responsible for propulsion.

“Almost certainly, the submarine is now out of action,” Sutton concluded.

He noted that the only place in the Black Sea where Russia could realistically hope to repair the damaged submarine would be the naval shipyard in occupied Sevastopol — the same dry docks where the submarine Rostov-on-Don was struck by Storm Shadow missiles in the fall of 2023.

Sutton emphasized that the consequences of the Novorossiysk strike are “far more strategic” than the damage to a single submarine — significant as that alone would be for Ukraine.

Russia currently relies on just two major Black Sea naval hubs, Sutton noted: occupied Sevastopol and Novorossiysk. Moscow was forced to withdraw much of its fleet from Sevastopol following repeated Ukrainian attacks and had considered Novorossiysk comparatively safe, aside from earlier Ukrainian strikes on fuel infrastructure.

That assumption no longer holds, Sutton said. Even inside the Novorossiysk base, Russian ships and submarines can no longer consider themselves secure.

“As a result, the Russians now face a dilemma,” he said. “They either have to significantly improve their defenses and accept they are no longer safe, or they have to relocate. But where?”

Sutton added that dispersing Russian naval assets could make them even more vulnerable, particularly given the limited capacity of smaller regional ports.

On Dec. 15, Ukraine’s Security Service said it carried out a unique special operation targeting the port of Novorossiysk. For the first time in history, Sub Sea Baby underwater drones detonated against a Russian Project 636.3 Varshavyanka-class submarine. Ukrainian officials said the blast caused critical damage, effectively disabling the vessel.

Analysts at the Institute for the Study of War said the strike could further degrade Russia’s ability to launch Kalibr cruise missile attacks against Ukraine, including targets in Odesa Oblast.