Unmanned submersible "Hailong III", on board the Chinese research vessel Dayang Yihao (Ocean No. 1), is examined by staff members of the scientific ocean expedition before being put into the sea for a deep sea testing on March 24, 2018. The submersible completed a 1,690-meter-deep sea testing in West Pacific Ocean, March 25, 2018. (Xinhua/Chen Hao)