Ukraine’s ‘Sub Sea Baby’ Strike: The End of Safe Harbours

On December 15, 2025, the rulebook for naval warfare was rewritten in the murky waters of the Black Sea. For the first time in recorded history, an uncrewed underwater vehicle (UUV)—specifically, a Ukrainian "Sub Sea Baby"—reportedly struck and disabled a submarine within the confines of a protected naval base. The target was no relic; it was the B-271 Kolpino, a state-of-the-art Russian Project 636.3 Kilo-class submarine, valued at roughly half a billion dollars.

The strike occurred at Novorossiysk, a port on the Russian mainland that Moscow had treated as a "safe haven" after its fleet was forced to retreat from Sevastopol in Crimea due to relentless missile and surface drone attacks. By bypassing surface defences and striking the submarine in its berth, Ukraine has demonstrated that geography and traditional booms are no longer sufficient shields against asymmetric threats.

For Australians, this distant conflict carries a stark, immediate warning. As the nation embarks on the historic AUKUS pathway to acquire nuclear-powered submarines and heavily invests in autonomous systems like the Ghost Shark, the events in Novorossiysk serve as a critical case study. It proves that even the most advanced, stealthy, and expensive assets are vulnerable to relatively cheap technology when moored at home.

The Incident: Disabling the ‘Black Hole’

The target of this historic operation was the B-271 Kolpino, a diesel-electric attack submarine often referred to by NATO analysts as a "Black Hole" due to its exceptional acoustic stealth capabilities. Commissioned in 2016, the Kolpino is a key asset in Russia's Black Sea Fleet, capable of launching Kalibr cruise missiles at land targets from submerged positions. These vessels are the backbone of Russia’s non-nuclear strategic projection in the region, making them a priority target for Kyiv.

The weapon of choice was the "Sub Sea Baby," a classified UUV developed by the Security Service of Ukraine (SBU). Unlike the "Sea Baby" uncrewed surface vessels (USVs) that hunt like wolf packs on the water's surface, this new variant operates fully submerged. Acting as a long-range loitering torpedo, it is designed to slip beneath radar horizons and visual lookouts.

While the Russian Ministry of Defence denied that any damage occurred, claiming the attack was repelled, independent analysis tells a different story. Surveillance footage, reportedly sourced from hacked harbour security cameras, shows a massive explosion near the submarine's stern. Subsequent satellite imagery revealed a crater on the concrete pier and the submarine riding lower in the water than usual, indicating potential flooding of internal compartments.

The navigational feat required to achieve this cannot be overstated. The UUV had to traverse hundreds of kilometres from Ukrainian-held territory, bypass layers of barges and nets placed at the harbour entrance specifically to stop surface drones, and execute a sharp terminal manoeuvre to strike the submarine's vulnerable propulsion section.

Strategic Shockwaves: The End of the ‘Safe Harbour’

The strategic implications of this strike extend far beyond the damage to a single hull. It effectively shatters the concept of the "safe harbour" in modern naval conflict.

Geography is No Shield

Following the sinking of the cruiser Moskva and repeated strikes on Sevastopol, Russia moved its most valuable assets, including the Kolpino, to Novorossiysk in the eastern Black Sea. The assumption was that distance would provide security. The arrival of long-range UUVs proves that sanctuary is now an illusion. If a drone can travel 1,000 kilometres autonomously and strike with precision, the rear echelon is now the front line.

The Repair Crisis

Perhaps more devastating than the immediate damage is the logistical trap the Kolpino now finds itself in. The strike reportedly targeted the stern, likely damaging the propeller, shaft, and hydroplanes. Such repairs typically require a dry dock and specialised heavy industry. However, the Black Sea Fleet’s main repair facilities in Sevastopol are under constant fire, and Novorossiysk lacks the necessary infrastructure for deep hull repairs.

Crucially, the submarine cannot leave the theatre. The Montreux Convention, enforced by Turkey, has closed the Bosphorus Strait to belligerent warships. The Kolpino cannot transit to St. Petersburg or the Baltic for repairs. It is effectively trapped in a combat zone with "irreparable" damage, rendering a $500 million asset useless for the duration of the war.

Asymmetric Economics

This operation highlights a brutal economic reality. A Varshavyanka-class submarine costs between US$400 million and US$500 million to replace. The drone used to disable it likely costs a fraction of that—potentially in the range of several hundred thousand dollars. In a war of attrition, the ability to trade cheap, unmanned systems for expensive, manned capital ships is a winning formula that challenges the procurement strategies of every major navy.

Lessons for Australia: AUKUS and Base Security

For the Australian Defence Force (ADF) and policymakers in Canberra, the smoke rising from Novorossiysk should be viewed as a signal flare. As Australia prepares to host rotational US and UK nuclear submarines (Submarine Rotational Force-West) and eventually acquire its own Virginia-class and SSN-AUKUS boats, the security of our naval bases is paramount.

Vulnerability of High-Value Assets

Nuclear-powered submarines are apex predators in the open ocean, but when moored at HMAS Stirling in Western Australia or maintenance facilities in Osborne, they are essentially stationary targets. The Kolpino incident demonstrates that surface booms and visual watches are insufficient against subsurface infiltrators. If a modified UUV can penetrate a Russian naval base on high alert during active war, Australian bases must be hardened against similar peacetime and grey-zone threats.

Defending the Subsurface Domain

The Royal Australian Navy (RAN) must look beyond surface protection. Harbour defence now requires a comprehensive "underwater sensor net" capable of detecting small, silent electric motors amidst the acoustic clutter of a busy port. This likely involves permanent seabed sonar arrays and patrol UUVs designed to intercept intruders before they reach the wharves.

Validation of the Ghost Shark

Conversely, this event validates Australia's own investment in asymmetric naval capabilities. The Ghost Shark program, a collaboration between the RAN, DSTG, and Anduril Australia, aims to field Extra-Large Autonomous Underwater Vehicles (XL-AUVs) [General context/Inference]. Ukraine's success with the Sub Sea Baby and Marichka drones proves that autonomous undersea warfare is not science fiction—it is a mature, lethal capability. For a middle power like Australia, possessing the ability to threaten adversary ports and shipping with UUVs provides a potent deterrent without risking Australian lives.

Local Expertise and Analysis

It is worth noting that Australian-connected experts are closely watching these developments. Reuben Johnson, a defence analyst who has consulted for the Australian government, highlighted that the damage to the Kolpino is likely structural and permanent due to the lack of specialized facilities. His assessment underlines the fragility of complex naval logistics—a lesson Australia must heed as it builds its own sovereign submarine sustainment capabilities.

The Future of Drone Warfare in the Indo-Pacific

The technology demonstrated in the Black Sea will not stay there. The proliferation of UUV technology is inevitable, and it will fundamentally alter the maritime security environment of the Indo-Pacific.

The "Shadow Fleet" War

Ukraine is not just targeting warships; it has used Sea Baby drones to strike oil tankers and infrastructure involved in Russia's "shadow fleet". This hints at a new form of economic naval warfare where commercial shipping can be targeted anonymously by subsurface drones. For an island nation like Australia, heavily reliant on maritime trade routes, the threat of unattributable UUV attacks on merchant shipping is a strategic nightmare that requires new defensive doctrines.

The 3D Threat Environment

Naval combat has shifted from a 2D surface fight to a 3D environment involving aerial drones, surface swarms, and now, underwater stalkers. Radar is effective against missiles and boats, but it cannot see underwater. The shift to subsurface kamikaze drones creates a threat vector that is incredibly difficult to detect and neutralise.

Conclusion

The strike on the B-271 Kolpino is a wake-up call for naval powers worldwide. While Ukraine fights for its survival, it is writing the textbook for 21st-century naval combat—a textbook that Australia must read carefully.

The era of the "safe harbour" is over. As we advance with AUKUS, we must ensure that our multi-billion dollar investments are not just formidable hunters in the deep ocean, but are also protected from the cheap, silent killers that can slip beneath the boom gate.

FAQ

What is the 'Sub Sea Baby' drone? It is a new Ukrainian uncrewed underwater vehicle (UUV), a submersible evolution of the surface 'Sea Baby' drone. It operates like a long-range, slow-moving torpedo capable of navigating harbour defences to strike ships below the waterline.

Was the Russian submarine destroyed? While not confirmed sunk, credible reports and satellite imagery suggest the submarine suffered critical damage to its stern, propeller, and potential pressure hull. Analysts believe it may be irreparable within the Black Sea due to a lack of dry dock facilities and the inability to leave the theatre.

Why is this strike considered historic? This is the first recorded instance in naval history of an uncrewed underwater vehicle (UUV) successfully striking and disabling a submarine in a combat zone.

How does this affect Australia? It highlights the vulnerability of expensive submarines when they are docked. It validates Australia's investment in underwater drones (like Ghost Shark) and emphasizes the critical need for upgraded sub-surface security systems at Australian naval bases like HMAS Stirling.

References:

Van Lokeren, F. (2025). Ukraine strikes Russian submarine with ‘Sub Sea Baby’ drone. Naval News. Available at: Naval News
Altman, H. (2025). Ukraine Claims World’s First Underwater Drone Attack On Russian Submarine. The War Zone. Available at: The War Zone
Johnson, R. (2025). ‘Impossible to Fix’: Russia’s Kilo-Class ‘Black Hole’ Submarines are An ‘Endangered Species’. 19FortyFive. Available at: 19FortyFive
Gosselin-Malo, E. (2025). Ukraine’s first underwater drone strike caught on hacked cameras. Defense News. Available at: Defense News

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