The Chinese research vessel Dayang Yihao (Ocean No. 1) returns to its base port after finishing a 215-day exploration of the Indian Ocean in Qingdao, east China's Shandong Province, June 18, 2015. During the 25,628-nautical mile voyage in China's 34th oceanic expedition mission, researchers on board the vessel explored the polymetallic sulfide resources on the sea bed. (Photo: Xinhua/Zhang Xudong)
