China will invest some $290 million to build an undersea defense system called the "Underwater Great Wall" beneath the South China Sea.

This wall will consist of underwater sensors intended to detect submarines and surface warships of the U.S. Navy and its allies at long-range.

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China disguised the true military nature of this program by first deploying underwater sensors in 2016 as a member of an ongoing international marine survey program named "Argo."

China deployed eight floating sensors in the South China Sea as part of Argo, a collaborative partnership of more than 30 nations. Linked together, the sensors provide a seamless global array allowing any country to explore the ocean environment.

Argo is a system for observing temperature, salinity and currents in the Earth's oceans and has been operational since the early 2000s. The real-time data it provides is used in climate and oceanographic research.

Some military analysts, however, say China's participation in Argo is intended to enhance its scientific knowledge about the disputed waters, especially what's beneath the surface, since the Chinese sensors have both civilian and military uses.

China plans to have 20 operational sensors about a meter beneath the surface of the South China Sea. China's sensors can monitor the underwater environment up to a depth of two kilometers.

Data from the sensors is transmitted to the mainland using China's BeiDou Satellite Navigational System that has numerous military uses. China's decision to use BeiDou and not the U.S. GPS to transmit data from its sensors also has military significance.

Chinese state-controlled television confirmed China's participation had a military aspect.

Jian Zhimin, a marine scientist at Shanghai's Tongji University, said the massive underwater observation system confirms China's status as an "ocean power" while a colleague said added the system was beneficial to "national defense."

Carl Thayer, a regional security analyst and emeritus professor at the University of New South Wales, said the system was "a further unilateral assertion of China's claim to indisputable sovereignty over the South China Sea."

He said China "could use the cover story for this undersea network to lay sensors designed to detect the movement of surface warships and submarines in particular."

A system such as this "mitigates the stealth advantage that submarines have. This would be of direct concern to the United States and other regional states that operate submarines."

Tagschina, Underwater Great Wall, South China Sea, underwater sensors, Argo