A nuclear submarine of the Chinese People's Liberation Army (PLA) Navy is seen during a naval parade of the PLA Navy warships and aircraft in waters off China's port city of Qingdao, east China's Shandong Province, on April 23, 2009. A Chinese officer introduces Chinese naval submarine to heads of delegations of foreign navies at Qingdao port, east China's Shandong Province, on April 22, 2009. [Xinhua]