Ukraine Claims Underwater Drone Crippled $500M Russian Submarine in Historic First

Ukraine’s Security Service (SBU) just announced what may be the most significant drone warfare milestone since the war began: the first-ever underwater drone attack on a submarine. We’ve been tracking Ukraine’s naval drone evolution for three years, from civilian DJI quadcopters to AI-enabled surface vessels. Now they’ve gone subsurface, and Russia’s “safe haven” at Novorossiysk isn’t safe anymore, if Ukrainian claims are accurate.

The attack, announced Monday, targeted a Project 636.3 Varshavyanka-class submarine (NATO designation: Kilo-class) docked at Novorossiysk, Russia’s primary Black Sea naval base. According to the SBU, the submarine sustained “critical damage and was effectively put out of action.”

Major outlets report that the port location in the SBU video has been verified, but the extent of damage to the submarine has not been independently confirmed and Russia disputes the claim. The timing is no coincidence: this strike was announced while President Volodymyr Zelenskyy sat in Berlin negotiating with Trump envoys Jared Kushner and Steve Witkoff, reports Politico.

The Sub Sea Baby: Ukraine’s New Underwater Weapon

The weapon responsible for this claimed historic strike is called the Sub Sea Baby, an underwater drone (UUV) that appears to be the subsurface cousin of Ukraine’s infamous Sea Baby surface drones. Both are named after SBU chief Vasyl Malyuk, whose name translates to “baby” in Ukrainian.

The SBU released video showing the attack. The footage pans across multiple Russian warships docked at Novorossiysk before an explosion erupts near the surfaced submarine, and independent media have geolocated the blast to the port area. The unmanned underwater vehicle is not visible in the footage, meaning it likely navigated a crowded harbor to strike a specific target if Ukraine’s account is correct.

“Ukraine’s underwater drone Sub Sea Baby attacked a Russian submarine,” the SBU stated. “The explosion critically damaged the submarine and effectively disabled it. The submarine was carrying four Kalibr cruise missile launchers, which Russia uses to strike at the territory of Ukraine.”

Politico notes that the media outlet could not independently verify the video or the reported level of damage. Russia’s Defense Ministry denied any damage occurred.

“Not a single ship or submarine as well as the crews of the Black Sea Fleet stationed in the bay of the Novorossiysk naval base were damaged,” the ministry claimed.

$500 Million Submarine vs. Asymmetric Drone Warfare

The financial implications of this strike are potentially staggering. According to the SBU and Ukrainian media, a Varshavyanka-class submarine costs approximately $400 million, and some Ukrainian officials suggest that, due to international sanctions restricting Russia’s access to high-tech components, building a replacement could now cost up to $500 million.

The Kilo-class submarine, nicknamed the “Black Hole” by Western navies due to its extremely quiet operation, represents one of Russia’s most capable non-nuclear submarine designs. It can carry up to four Kalibr cruise missiles, the same weapons Russia has repeatedly used to strike Ukrainian cities, power plants, and civilian infrastructure.

If the SBU’s claims are accurate, this single drone mission eliminated, at least for the foreseeable future, not just a platform Ukraine values at roughly $400–500 million but also a strategic Kalibr launch capability.

Russia’s Black Sea Fleet originally operated six Improved Kilo-class submarines; one, the Rostov-on-Don, was severely damaged by a Ukrainian Storm Shadow missile strike in Sevastopol in September 2023 and struck again in August 2024, and some analysts say this latest attack could leave only four fully operational Kilo-class boats in the Black Sea.

From Sevastopol to Novorossiysk: Nowhere Is Safe

The strategic significance of this attack cannot be overstated if the damage assessment holds. Ukraine’s surface drones, particularly the Sea Baby and Magura V5, have already inflicted massive damage on Russia’s Black Sea Fleet and helped force Moscow to relocate key assets. As we reported in October, upgraded Sea Baby drones forced Russia to relocate its primary naval base from Sevastopol in Crimea to Novorossiysk on the Russian mainland.

Russia thought Novorossiysk was safe. It sits on Russian territory, far from Ukrainian-held positions. But this claimed underwater attack suggests that even “safe” ports are now within reach of Ukraine’s expanding drone capabilities.

“The targeted submarine had been forced to remain in the port of Novorossiysk due to successful operations by Sea Baby surface drones, which drove Russian ships and submarines out of Sevastopol Bay,” the SBU stated.

Russian military bloggers acknowledged at least a serious threat. Boris Rozhin, a pro-war analyst, wrote on Telegram that if the strike report was accurate, it “points to a serious failure in the organisation of the harbour’s defences” and noted that Ukraine “appears to have an upper hand in the harbour in Novorossiysk.”

Timing Is Everything: Strike Capability as Leverage

The attack coincided with critical peace negotiations in Berlin. Zelenskyy met with Trump’s envoys for over five hours on Sunday and continued talks on Monday, according to reporting from Berlin. During a statement at the German-Ukrainian economic forum, Zelenskyy explicitly connected Ukraine’s strike capability to its negotiating position.

“While diplomatic processes and negotiations are underway that could bring the end of the war closer, we must not forget that Russian strikes continue every day,” Zelenskyy said. “Putin is using the brutality of the strikes as leverage in negotiations.

He continued: “Our ability to recover from strikes, our ability to produce weapons and strike back, our ability to shoot down Russian missiles and drones, are our leverage in negotiations.”

The message could not be clearer. As Trump pushes for a quick settlement and reportedly pressures Ukraine to cede territory, Kyiv is demonstrating that it can still inflict significant damage on Russian military assets, at least according to its own and Western-aligned accounts. A submarine that Ukraine values in the $400–500 million range is a powerful statement.

DroneXL’s Take

This attack represents, if independently confirmed, the completion of Ukraine’s multi-domain drone revolution. We’ve tracked this evolution from the earliest days of the invasion, when Ukraine’s Ministry of Defense asked citizens to bring their consumer drones to help monitor Russian movements. Three years later, Ukrainian drones dominate land, sea, air, and now claimed subsurface operations.

Back in August 2023, we covered Ukraine’s unveiling of the Marichka underwater drone. At the time, experts noted that underwater drones could hit ships on their vulnerable underwater sections, potentially causing more damage than surface strikes. The Sub Sea Baby appears to be the combat-proven result of that development program, if Ukrainian battlefield reporting is borne out over time.

The broader implications extend far beyond this single submarine. As we reported in May, Ukraine’s drone innovations are reshaping modern warfare and inspiring NATO.The alliance is now racing to adopt Ukrainian tactics, including interceptor drones and naval drone doctrine, and this underwater strike claim will only accelerate that process.

Russia’s denial is predictable but important to note. The SBU has a strong track record of claims later supported by imagery and Western intelligence, and geolocated video supports that a large explosion occurred near a submarine at Novorossiysk, while independent outlets stress that the actual damage level remains unverified. Even Russian military bloggers acknowledged the strike as a serious warning.

The economics tell the real story. A drone that likely costs a fraction of a cruise missile appears to have at least disabled, according to Ukraine, a submarine platform valued in the hundreds of millions of dollars and carrying strategic weapons. This is asymmetric warfare at its most effective, and it validates the $2.3 billion U.S. investment in Ukraine’s military drone development program in the eyes of its proponents.

What do you think about Ukraine’s underwater drone capability? Does this change the calculus for peace negotiations? Share your thoughts in the comments below.