Defense Express reported the information.The identification came after Russian authorities attempted to downplay the damage by releasing limited footage of the vessel. Ukrainian open-source analyst Duke BG cracked the case by examining subtle markings near the submarine's aft hatch, which distinguished the Kolpino from its sister ships through a distinctive thin white border, unlike the thicker circular markings found on the B-265 Krasnodar and B-268 Veliky Novgorod.Not 100% sure, but I've deduced that the submarine that was hit recently in Novorossyisk by SubSeaBaby was B-271 Kolpino.(based on a splotch of paint)Unless my info on the two outside Black sea is wrong, because they almost fit too. https://t.co/jJNz2aVawA pic.twitter.com/TZimlecOPR— Duke BG (@duke_garland_2) December 17, 2025 The B-271 Kolpino represents a significant loss for Russia's Black Sea Fleet. Launched on May 31, 2016, and commissioned that November, it is the most recently constructed Project 636.3 submarine assigned to the region. Defense analysts note this makes it "the best of three possible options" from Ukraine's strategic perspective.The joint operation by Ukraine's Security Service and Naval Forces caused extensive damage to the port infrastructure, creating a crater approximately nine meters in diameter at the pier. Satellite imagery captured on December 16 showed the stricken submarine sitting more than a meter deeper in the water than its normal waterline before salvage crews pumped it out.Intelligence officials are now working to assess potential damage to a second submarine located several hundred meters from the blast site, which may have sustained harm to its sonar systems from the force of the explosion. With the previously destroyed B-237 Rostov-on-Don and now the critically damaged Kolpino, Russia's Black Sea submarine capabilities continue to diminish.