A marine surveillance helicopter flies over the Ganquan Island, an uninhabited island of the Xisha Islands in the South China Sea, March 11, 2013. Crew members aboard the Chinese marine surveillance ship Haijian 262 patrolled the Ganquan Island on Monday. (Xinhua/Wei Hua)

A marine surveillance officer notes down geographical information at a ruin on the Ganquan Island, an uninhabited island of the Xisha Islands in the South China Sea, March 11, 2013. Crew members aboard the Chinese marine surveillance ship Haijian 262 patrolled the Ganquan Island on Monday. (Xinhua/Wei Hua) 

Marine surveillance officers investigate an ancient well and the water in it on the Ganquan Island, an uninhabited island of the Xisha Islands in the South China Sea, March 11, 2013. Crew members aboard the Chinese marine surveillance ship Haijian 262 patrolled the Ganquan Island on Monday. (Xinhua/Wei Hua)