CaliToday (17/12/2025): In a feat of naval warfare that may rewrite military textbooks, Ukraine has claimed a historic "first." The Security Service of Ukraine (SBU) recently announced a successful strike against a Russian Project 636.3 "Varshavyanka" (NATO reporting name: Kilo-class) submarine using a revolutionary underwater drone: the "Sub Sea Baby."
Photo credit: Ukraine's Security Service (SBU)
This operation, conducted at the Russian naval base in Novorossiysk, marks a massive shift in maritime strategy. For the first time in history, an autonomous underwater vehicle (AUV) has successfully engaged and severely damaged a submarine in port.
The Target: Russia’s "Black Hole"
The Project 636.3 "Varshavyanka" is no ordinary vessel. Often referred to by the U.S. Navy as the "Black Hole" because of its incredibly low acoustic signature, it is designed for anti-submarine and anti-ship warfare.
Strategic Threat: These submarines are equipped with four launchers for Kalibr cruise missiles, which have been used extensively to strike Ukrainian civilian infrastructure from the safety of the Black Sea.
The Price Tag: While Ukraine previously valued these vessels at $400 million, current international sanctions and supply chain disruptions have driven the replacement cost of a new unit to an estimated $500 million.
Technical Edge: An evolution of the 1980s Soviet Project 877, the 636.3 variant is faster, quieter, and boasts a significantly longer striking range.
The Weapon: "Sub Sea Baby"
While Ukraine’s surface drones (Sea Baby) have already terrorized the Russian Black Sea Fleet, the Sub Sea Baby represents a new evolution. By moving the strike capability underwater, Ukraine has bypassed traditional surface defenses and visual surveillance.
"This was a joint operation between the 13th Main Department of Military Counterintelligence and the Ukrainian Navy," the SBU stated. The explosion reportedly left the submarine "nearly incapacitated."
Comparison: A New Milestone in Naval History
This victory is being hailed as the most significant Ukrainian naval achievement since the sinking of the cruiser Moskva in 2022.
| Feature | The Moskva (Cruiser) | The Varshavyanka (Submarine) |
| Significance | Sinking of the Black Sea Fleet Flagship | First-ever drone strike on a submarine |
| Weapon Used | Neptune Anti-ship Missiles | Sub Sea Baby Underwater Drone |
| Impact | Ended Russian dominance in the NW Black Sea | Neutralized a stealthy Kalibr missile carrier |
| Estimated Cost | ~$750 Million | ~$500 Million |
Why This Matters
The successful strike in Novorossiysk a port previously thought to be a "safe haven" after the retreat from Sevastopol proves that Russia’s undersea assets are no longer untouchable. By neutralizing a Kilo-class submarine, Ukraine has effectively removed a major source of missile strikes while demonstrating that even the world's quietest submarines cannot hide from innovative, low-cost drone technology.