China's unmanned submersible "Hailong III" dives to 4,266 meters under sea

Workers attach a flotation device to China's unmanned submersible "Hailong III" for a deep water test, on April 4, 2018. China's unmanned submersible "Hailong III" dived 4,266 meters below the sea surface in the western Pacific Ocean late Wednesday while conducting a 4,500-meter level deep water test. (Xinhua/Chen Hao)