China Tests Giant Uncrewed “Submarine-Drones” off Hainan

In recent weeks, evidence has emerged that the Chinese Navy (PLAN) is conducting secret trials of two enormous uncrewed submarines near Hainan Island, in the South China Sea. These underwater drones are far larger than what most navies currently operate, and their deployment signals a bold leap in undersea warfare. Here is a clearer, up-to-date look at what is known so far — and why it matters.

What is happening?

• China is testing two giant underwater drones of approximately 40–42 meters in length, placing them in the same size class as many crewed attack submarines.

• These vessels are uncrewed — that is, autonomous or remotely operated — rather than conventional manned submarines.

• They are being stationed in floating docks rather than in conventional submarine pens or on quay walls. One dock, named Zhuan Yong Fu Chuan Wu 001 (Special Floating Dock 001), was completed in 2024 and has already been used to move one of the new underwater drones.

• The floating docks allow the drones to be launched, recovered, hidden, or transported away from busy ports, reducing detection risk and logistical constraints.

• The drones are currently test-operating in waters off Gangmen Harbour and Yinggezui, on the western coast of Hainan near Sanya.

• These new vessels appear to lack a traditional sail (conning tower) and feature X-shaped rudders at the stern — design features more akin to advanced submarine hulls than small underwater drones.

• The 705 Research Institute (part of China Shipbuilding Industry Corporation, CSSC) is believed to be involved in their development.

Why is this significant?

1. A new class beyond ‘XLUUV’

Navies in the West currently use or explore XLUUVs (extra-large uncrewed underwater vehicles). But at this scale — some 10–20 times the size of those — China’s vessels challenge the limits of what “XL” implies. Some analysts propose new labels such as XXLUUV or Ultra-Large UUV to reflect their scale and capabilities.

Because they are so big, their roles are expected to be richer and more complex than those of standard underwater drones:

• They may carry large payloads of weapons (torpedoes, mines, missiles) or specialized sensors.

• Their sensor suites may approach the strength of manned submarines, with more powerful sonar or intelligence equipment.

• Without the constraints of space and life support for a crew, their volume can be dedicated more fully to payloads, energy storage, and autonomy systems.

2. Stealth, surprise, and strategic flexibility

By using floating docks, China can conceal operations, appear to shift the docks away from port when needed, and avoid interference with normal shipping and port traffic. It’s a way to maintain operational secrecy and flexible deployment.

China’s experiment may stretch how navies think about unmanned submarine warfare: large-scale drones functioning as force multipliers in the undersea domain, operating alongside conventional submarines, surface ships, and drones.

3. China is moving fast — and at scale

While many Western navies and defense firms are only now ramping efforts to field large underwater drones, China appears significantly ahead in both ambition and investment. The appearance of two large prototypes (or competing designs) shows China is not just experimenting, but entering a serious contested domain in underwater robotics.

Moreover, China already has a spectrum of XLUUV programs known or inferred from open sources, possibly five or more types under development. The new vessels seem to represent a higher, more ambitious tier in that hierarchy.

4. Strategic implications for regional and global navies

• These drones could complicate surveillance, anti-submarine warfare, and undersea domain control for rival powers in the region.

• They raise the bar for counter-drone and detection systems: dealing with an ever larger, more stealthy, and potentially armed drone submarine is far more demanding than countering small UUVs.

• In strategic hotspots like the Taiwan Strait or the South China Sea, they could be used to lay mines, conduct covert surveillance, or interdict undersea communications — without risking a human crew.

• Western navies will likely feel pressure to accelerate their own programs for large underwater drones, invest more in detection and countermeasures, and rethink submarine fleet structure and tactics.

What is still uncertain (and what to watch)

• Propulsion: It is unclear whether these vessels use diesel engines, large battery systems, fuel cells, or hybrid systems. There is currently no credible evidence they are nuclear-powered.

• Autonomy and control: The AI, autonomy, navigation, and decision systems must be highly advanced to allow them to operate reliably undersea.

• Exact payloads: While torpedoes, mines or missiles are plausible, how many and what kind remain speculative.

• Operational patterns: How far they will patrol, whether they will launch from mother ships or from coastal facilities, and how they integrate with manned assets remain to be seen.

• Public reveal: China may reveal these or similar drones in future parades or defense expos. Observers are also watching if more floating dock assets appear at Hainan or elsewhere.

China’s testing of these giant uncrewed submarines signals a potential shift in undersea warfare. Rather than simply scaling up existing drone designs, China seems to be creating a new class of vessel — one that blurs the line between autonomous underwater vehicle and full-fledged submarine.

If they become operational, these drones could change how navies project undersea power, structure their fleets, and defend sea lanes. The world is entering a new era where uncrewed platforms may become peer competitors in the deep.