Japan Evaluates French and American Underwater Gliders to Boost Maritime Defense

The Japan Maritime Self-Defense Force (JMSDF) has taken a significant step in modernizing its underwater surveillance capabilities by acquiring two advanced underwater gliders for evaluation. The service has received the SeaExplorer X2 from French company Alseamar and the Slocum G3 from American firm Teledyne Webb Research. These unmanned underwater vehicles (UUVs) will be tested for their effectiveness in oceanographic research and potential defense applications.

Why Japan is Investing in Underwater Gliders

Japan is strengthening its undersea warfare capabilities as tensions rise in the region, particularly near the Nansei Islands and the Senkaku Islands, areas of strategic importance due to China's increasing maritime activities. Underwater gliders play a crucial role in gathering oceanographic data, which is essential for detecting and tracking submarines, monitoring acoustic conditions, and improving naval operations.

The JMSDF aims to integrate autonomous UUVs into its maritime defense strategy. The newly acquired SeaExplorer X2 and Slocum G3 will be used to study water temperature structures and assess their suitability for long-term deployment.

How These Underwater Gliders Work

SeaExplorer X2 (France)

The SeaExplorer X2 is a multi-mission underwater glider that moves autonomously without the need for a traditional engine or propeller. It shifts its center of gravity using an internal lithium-ion battery, enabling precise underwater navigation. When it surfaces, it communicates with satellites, transmitting data and receiving updates. Its modular design allows it to be equipped with different sensors for specific missions.

Slocum G3 (USA)

The Slocum G3 is another autonomous underwater glider capable of diving up to 1,000 meters deep. It utilizes a buoyancy control mechanism and a shifting battery to glide underwater for extended periods. It can be remotely controlled and updated via satellite communication, making it an ideal tool for long-term ocean observations and potential defense applications.

Japan’s Plan for These UUVs

The JMSDF will conduct independent research on these underwater gliders until March 2026, with the goal of selecting the most suitable model for future operations. Initial tests were planned as performance trials, but the Navy shifted to an independent research approach since both gliders are already commercially available.

A long-term objective is to build a fleet of 10-12 underwater gliders by 2030-2032, potentially for use in oceanographic research and underwater warfare. These UUVs could play a role in acoustic intelligence and anti-submarine missions, further strengthening Japan’s naval capabilities.

While the Slocum G3 benefits from being the most widely used underwater glider globally, the SeaExplorer X2 has an advantage due to its existing presence in Japan, with several units already operated by civilian organizations.

Future Expansion: Seafloor Mapping and Underwater Surveillance

Beyond monitoring water temperatures, Japan is also considering acquiring UUVs for seafloor topography surveys and acoustic research. The JMSDF has allocated 200 million yen ($1.35 million) in its 2024 budget for research into maritime observation UUVs. A contract for further study and sample selection will be signed before March 2025, with a trial model expected to be chosen in the following fiscal year.

Strengthening Japan’s Maritime Security

Japan’s investment in underwater gliders is part of a broader effort to counter growing regional challenges. Military analysts believe that in the future, Japan may use UUVs for mine warfare and anti-submarine operations, particularly around the Miyako Strait, a key waterway for Chinese naval movements.

As China continues to expand its naval presence in the East China Sea, the JMSDF is preparing to leverage cutting-edge technology to enhance underwater situational awareness and maritime security. The ongoing evaluation of these gliders marks the beginning of a larger push toward integrating autonomous systems into Japan’s maritime defense strategy.