China Plans East China and South China Sea Underwater Surveillance Networks

China has a program to build underwater surveillance networks in the East China Sea and South China Sea.  The networks cost approximately two billion yuan with a planned construction period of five years. The networks include a number of unspecified sensors installed on the ocean floor that are connected via optical cables to a monitoring station in Shanghai. This will allow China to around-the-clock, real-time, high-definition, multiple interface, and three-dimensional underwater surveillance.

China is already able to conduct regular surveillance of the airspace and sea surface using advanced radars, unmanned aerial vehicles and Gaofen 3 satellites.

CNN

CCTV