Photo taken on July 15, 2016 shows the lifeboat on the "Zhang Jian", a Chinese deep-sea explorer ship. The ship, 97 meters long and 17.8 meters wide, set sail on July 12 from Shanghai to the South Pacific for scientific research. It's the mother ship of the 11,000-meter Rainbow Fish submersible, which Chinese researchers are preparing to send to the Mariana Trench late this year or early next year. Photo:Xinhua

Photo taken on July 15, 2016 shows the hanger on the stern of the "Zhang Jian", a Chinese deep-sea explorer ship. Photo:Xinhua

Photo taken on July 15, 2016 shows the hanger on the stern of the "Zhang Jian", a Chinese deep-sea explorer ship. Photo:Xinhua

Liu Dongsheng (front), staff member of the "Zhang Jian", a Chinese deep-sea explorer ship, stays on duty at the engine control room on the ship, July 15, 2016. Photo:Xinhua

Li Tao, staff member of the "Zhang Jian", a Chinese deep-sea explorer ship, patrols in the engine room on the ship, July 15, 2016. Photo:Xinhua

Wang Jiquan, staff member of the "Zhang Jian", a Chinese deep-sea explorer ship, works at the engine room on the ship, July 15, 2016. Photo:Xinhua

Chef Bo Weiju, staff member of the "Zhang Jian", a Chinese deep-sea explorer ship, prepares dinner at a kitchen on the ship, July 15, 2016. Photo:Xinhua

Staff members of the "Zhang Jian", a Chinese deep-sea explorer ship, work at the engine control room on the ship, July 15, 2016. Photo:Xinhua

Photo taken on July 15, 2016 shows the living area of the "Zhang Jian", a Chinese deep-sea explorer ship. Photo:Xinhua

Chef Yang Hongzhong, staff member of the "Zhang Jian", a Chinese deep-sea explorer ship, cooks at a kitchen on the ship, July 15, 2016. Photo:Xinhua