Satellite images and open-source intelligence reveal that the People’s Liberation Army Navy (PLAN) is testing two massive uncrewed submarines off Hainan Island in the South China Sea. At over 40 meters long, these machines are about the size of a crewed attack submarine—and ten to twenty times larger than the uncrewed submarines the United States and Europe are experimenting with.

The Naval Warfare of the Future is Unmanned

Naval News reported that the two submarines are based at floating docks near Gangmen Harbour, close to Sanya — the PLAN’s major nuclear submarine base. Unlike smaller drones that can be craned into the water, these giants need their own floating docks to conceal and deploy them. One dock, called Zhuan Yong Fu Chuan Wu 001, was only launched in late 2024.

The reason for all this secrecy is easy to guess: these vessels are unlike anything else in the world.

“These extra-large UUVs could also carry payloads capable of overcoming coastal defences, a critical feature given the tensions in China’s immediate waters, from the Taiwan Strait to the South China Sea,” said Thomas Lim, an associate research fellow at Singapore’s S. Rajaratnam School of International Studies, in Asian Military Review.

Western militaries call their biggest drones “XLUUVs” — extra-large uncrewed underwater vehicles. But China’s newest models blow that definition apart. They may need a new category altogether: XXLUUVs, or ultra-large drones.

From the outside, the new drones already look the part. Satellite images show vessels about 40–42 meters long, with sleek hulls, no sail or tower, and X-shaped rudders at the stern. Their form echoes true submarines more than drones.

Their size suggests they can carry torpedoes, mines, or even vertical-launch missiles. A conventional submarine of similar size can host eight heavyweight torpedoes. Without humans to feed, clothe, and oxygenate, that same volume could be crammed with more weapons — or other payloads limited only by budget.

The drones’ power sources are still a mystery. Their dock arrangement suggests they don’t rely on exotic fuels like liquid oxygen. So, analysts suspect they run on huge banks of lithium batteries, diesel-electric engines, or both. There’s no evidence of nuclear propulsion (yet) but the speculation is inevitable.

Inside, these machines could hide sensor suites closer to those of crewed submarines than to drones. Larger hulls mean room for advanced sonar, towed arrays, and high-power electronics. Without crew to analyze the data, they must lean heavily on AI to sift through ocean noise, spot threats, and maybe even make combat decisions in real time.

Innovation at Speed

What’s striking is how fast China has moved. In 2019, the PLAN rolled out its first public uncrewed sub, the HSU-001. That model focused on intelligence gathering, with propellers designed for slow cruising and external mounts for sensors.

Since then, Beijing has churned out at least five different designs, including the AJX002, a sleek drone with pump-jet propulsion for stealth that looks like an oversized torpedo, and the UUV-300 family, which can be armed with torpedoes or mines. Some models, like the HSU100, are built for surveillance. Others are clearly designed to take down ships.

This diversity shows China is pursuing a prototyping approach, building multiple designs in parallel to speed up innovation. The U.S., by contrast, has invested heavily in just one major project: the Orca XLUUV, a single design with a 6,500 nautical-mile range.

China’s method has a Silicon Valley feel to it: try many options, fail fast, and scale up what works. That means they can test specialized designs for seabed warfare, undersea infrastructure sabotage, or rapid deployment from shipping containers. Western analysts worry this pace could leave the Pentagon flat-footed.

The potential missions could involve seabed warfare: attacks on undersea fiber-optic cables, oil pipelines, or other critical underwater infrastructure. Attacks on underwater fiber-optic cables — the arteries of the global internet — are a particularly growing concern. An uncrewed submarine the size of a traditional attack boat, packed with sensors and robotic arms, could slip down to the seabed and cut or tamper with these networks. Previously, ZME Science reported how China, in a rare moment of admission, unveiled a high-tech cutting tool capable of operating at unprecedented depths of up to 4,000 meters — twice as deep as existing cable infrastructure typically extends.

As Naval News‘s H I Sutton put it: “It seems inevitable that uncrewed submarines will increasingly encroach on the domain of traditional submarines. … This is a new world which China seems much more willing to embrace.”

For decades, the assumption was that China’s subs were decades behind Western ones. That idea is sinking fast.