One area where unmanned underwater vehicles (UUV) and unmanned surface vehicles (USV) would make a splash is in Chinese anti-submarine warfare (ASW) efforts. ASW capabilities have been a longstanding weak spot for the PLAN, leaving it at a disadvantage to American and Japanese attack submarines. As a response, the China State Shipbuilding Corporation (CSSC), which builds virtually all PLAN warships, has proposed an "Underwater Great Wall" of sensors, positioned on the seabed floor, to listen for enemy submarines. (The US had a similar system on the Atlantic Ocean floor to listen for Soviet submarines.) Such underwater listening posts may already have been installed near the giant PLAN base at Sanya, Hainan Island in the South China Sea. On a more optimistic note, CSSC suggested that an Underwater Great Wall would be useful for warning against natural disasters like tsunami, and could be used to collect research data on marine life and geology.