A drill of seven vessels, including China's largest fishery patrol ship, China Yuzheng 311, and a helicopter is held in Sanya, south China's Hainan province to mark the 5th signing anniversary of the Demarcation Agreement on Beibu Bay, signed by China and Vietnam, June 30, 2009. China will intensify patrols in the South China Sea to protect its fishermen amid a rising tide of disputes with neighboring countries, an official said Tuesday.[CFP]