An underwater technology demonstrator was launched in Plymouth, created in the interests of the Royal Navy of Great Britain to pave the way for future ultra-large uninhabited underwater vehicles of the XLUUV type. According to Naval News, testing of the sample will begin next month.
The experimental underwater vehicle was built by MSubs as part of the CETUS project. MSubs received a corresponding contract worth 15.4 million pounds in November 2022.

XLUUV type underwater vehicle, United Kingdom
Turnchapel Wharf

XLUUV type underwater vehicle, United Kingdom
Turnchapel Wharf
The CETUS project is funded through the British Spearhead Anti-Submarine Warfare (ASW) program. This development should reduce the risks associated with the acquisition of future large-scale underwater drones and their payloads, as well as help the Royal Navy test possible use cases for XLUUV, including submarine warfare, reconnaissance and surveillance.
The length of the launched demonstrator is 12 meters, diameter is 2.2 meters, weight is up to 25 tons with a full test payload. Allegedly, the MSubs product is now the largest and most complex unmanned underwater vehicle purchased by the European fleet.
In addition to testing various payload modifications, the CETUS project should strengthen confidence in long-term autonomous operations. In the current configuration, the demonstrator will be able to stay at sea for up to five days, but the design allows the integration of additional batteries to increase autonomy.
The leading naval power in the world, including the US, China, Russia, the UK, Japan and Germany, are developing in the field of large underwater drones class XLUUV. However, only a few of them are implementing projects for combat modifications of such devices, limited to surveillance and reconnaissance systems. Even the well–known American device of this type, ORCA, is limited in combat capabilities - it is only capable of exposing mines.
India and China have announced the development of combat XLUUVs. In June 2023, at the MADEX exhibition in Busan, the South Korean company Hanwha Ocean presented a project for an ultra-large underwater drone with two torpedo tubes. In January 2024, the Naval Group entered into a framework agreement with the General Directorate of Armaments (DGA) of France for the design, production and testing of a UCUV-type unmanned combat underwater vehicle demonstrator.