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Ukraine’s “Sub Sea Baby” Drone Cripples $400M Russian Submarine in Black Sea Port
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Ukraine’s Security Service (SBU) said it carried out a special operation in Russia’s Black Sea port of Novorossiysk, using “Sub Sea Baby” underwater drones to strike a “Varshavyanka”-class submarine. The claim, if confirmed, would underline how Ukraine’s expanding sea-drone campaign is pressing Russia to shift high-value naval assets away from occupied Crimea and deeper into Russian ports.
The SBU said on December 15 that the drone strike targeted a Russian Project 636.3 Varshavyanka-class (NATO: Improved Kilo-class) submarine, reportedly inflicting critical damage that rendered the vessel inoperable. The submarine was said to carry four Kalibr cruise missile launchers used in attacks on Ukraine.
According to the SBU, the explosion inflicted critical damage and the submarine carried four launchers for Kalibr cruise missiles used in strikes on Ukraine.
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“As a result of the explosion, the submarine suffered critical damage and was effectively put out of action,” the SBU said in a statement.
⚡️BREAKING: Ukraine just made naval warfare history.
— UNITED24 Media (@United24media) December 15, 2025
Ukraine’s Security Service hit a Russian Kilo-class submarine in Novorossiysk using Sub Sea Baby underwater drones, leaving the sub critically damaged and effectively knocked out, the SBU reports. pic.twitter.com/VkrXDhOzGH
The SBU stated that the operation was conducted jointly by its 13th Main Directorate of Military Counterintelligence and the Naval Forces of Ukraine, and estimated the submarine’s value at approximately $400 million.
The agency added that constructing a comparable replacement could cost up to $500 million under international sanctions.
Earlier, it was reported that the SBU showcased updated “Sea Baby” sea drones in multiple weapon configurations and said its maritime drones have repeatedly struck Russian ships and damaged the Crimean Bridge.
