China is quietly building an undersea capability that looks unlike anything currently fielded at scale in the West.

A second dedicated mothership for extra-extra large uncrewed underwater vehicles, or XXL UUVs, has now been launched in Guangzhou. Its purpose appears highly specialized: carry, support, launch and recover some of the largest uncrewed submarines known to be under development anywhere in the world.

The most striking feature is the ship’s stern.

Instead of relying on a conventional crane or side-launch system, the vessel uses a large submarine lift that can be lowered directly through an opening in the bottom of the ship. This allows an uncrewed submarine to be moved between the sea and an internal support area while remaining protected by the mothership itself.

That is not a small design choice.

It suggests these ships were built from the beginning around the operation of large underwater vehicles.

The new vessel is not identical to the first mothership built in Shanghai. Although both share the same basic layout and the distinctive submarine lift, the second ship is somewhat smaller. It is estimated at around 180 meters long, compared with roughly 205 meters for the earlier vessel.

It also appears to have fewer decks and a shallower draught, which likely means a lower displacement.

But calling it smaller can be misleading.

At around 180 meters, this is still a very large support vessel. Its dimensions suggest it could carry substantial equipment, maintenance facilities, command-and-control systems and potentially multiple underwater vehicles.

The more important question is what exactly these ships are supporting.

China is believed to be testing at least two classes of very large uncrewed submarines. One is estimated to be around 35 meters long, while another may reach roughly 45 meters.

Those dimensions put them in a very different category from the small UUVs commonly used for mine countermeasures, survey work or reconnaissance.

They are closer to small submarines than conventional underwater drones.

According to the information currently available, both types may be armed. If that is correct, their potential missions could extend far beyond intelligence gathering.

Large autonomous submarines could theoretically be used for surveillance, seabed operations, mine warfare, anti-submarine missions or long-range strike support. Their size also gives them more space for batteries, sensors, communications equipment and payloads.

The comparison with Boeing’s Orca XLUUV shows just how unusual the Chinese systems may be.

Orca is already considered a large autonomous underwater vehicle, but the Chinese designs described here are reportedly many times larger. If the size estimates are accurate, Beijing is experimenting with a class of undersea system that pushes autonomous naval warfare into a new scale.

The motherships are what make that capability even more significant.

A huge uncrewed submarine is only useful if it can be deployed, recovered, maintained and supported efficiently. Dedicated support vessels solve part of that problem.

They can extend operational range, move UUVs closer to mission areas and provide maintenance without requiring the underwater vehicles to return to a fixed naval base after every deployment.

That could create a much more flexible undersea force.

It also reflects a broader trend in Chinese naval development: building not just individual platforms, but complete ecosystems around new technologies.

One XXL UUV is an experiment.

Two dedicated motherships begin to look like infrastructure.

That distinction matters.

The real strategic signal may not be the existence of one giant underwater drone, but China’s willingness to invest in the ships needed to operate such systems repeatedly and at scale.

The next phase of naval competition may therefore happen below the surface, with fewer crews, more autonomy and increasingly large unmanned platforms.

China appears determined to explore that future early.

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