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KYIV/NOVOROSSIYSK—In a dramatic escalation of the Black Sea naval war, Ukraine has claimed a historic and successful strike on a Russian Project 636.3 Varshavyanka-class (Kilo-class) attack submarine docked at the heavily guarded Russian naval base of Novorossiysk.
The Security Service of Ukraine (SBU) stated that the operation, conducted jointly with the Ukrainian Navy, was executed by a novel, domestically produced uncrewed underwater vehicle (UUV), which they have dubbed “Sub Sea Baby.”
A Blow to Russia’s ‘Safe Harbor’
The submarine, known in NATO as the “Improved Kilo” class and often nicknamed the ‘Black Hole’ for its stealth capabilities, is a crucial asset for Russia’s Black Sea Fleet, capable of carrying the feared Kalibr cruise missiles that have frequently been launched against Ukrainian cities.
According to the SBU, the submarine suffered “critical damage” and is “effectively put out of action.” The strike is particularly significant as Novorossiysk, on the Russian mainland, has served as a critical relocation point for the Black Sea Fleet after successful Ukrainian surface drone attacks forced many Russian vessels out of the Crimean port of Sevastopol. The breach of this seemingly safer harbor signals a profound new threat to Moscow’s naval operations.
An advisor to President Volodymyr Zelenskyy noted that this marks the first time in history an underwater drone has successfully neutralized a submarine—an act that redefines the potential of uncrewed warfare in the maritime domain.
Battle of the Claims
Footage released by the SBU purportedly shows a powerful explosion erupting near the pier where the submarine was moored. Analysts have matched the location to the Novorossiysk port layout, lending credence to Kyiv’s claims.
However, Moscow swiftly and categorically denied any damage. The Russian Black Sea Fleet issued a statement acknowledging an attempt at sabotage but asserted that “No ships or submarines stationed at the Novorossiysk naval base, nor their crews, sustained any damage and they are continuing their duties as usual.”
Despite the denial, a Ukrainian Navy spokesperson framed the operation as “another turning point” in the naval conflict, highlighting that a submarine is arguably the most difficult naval target to hit. The estimated cost of a Varshavyanka-class submarine is around $400 million, a figure Kyiv suggests could be significantly higher to replace under current international sanctions.
The ability of the ‘Sub Sea Baby’ to penetrate the fortified defenses of a major Russian naval base and strike a submarine—an inherently stealthy target—demonstrates not only Ukraine’s remarkable technological innovation but also the expanding reach of the war into key Russian strategic infrastructure.
