Photo taken by the unmanned submersible Haima shows a joint deep-sea work in a cold seep area in the South China Sea. China has carried out deep-sea research with two submersibles to explore a cold seep in the South China Sea, according to a statement released by the China Geological Survey's Guangzhou branch Wednesday. It is the first time two domestically-made deep-sea submersibles, the unmanned submersible Haima (Seahorse) and manned submersible Shenhai Yongshi (Deep Sea Warrior), have been used in a single scientific expedition. (Xinhua)