A crew member of Tansuo-2, the second mother ship of China's new deep-sea manned submersible Fendouzhe (Striver), disembarks from the vessel in Sanya, south China's Hainan Province, Dec. 21, 2020. China's scientific research ship Tansuo-2 returned to port in the city of Sanya, south China's Hainan Province on Monday, after completing its ocean expedition. (Xinhua/Zhao Yingquan)

Tansuo-2, the second mother ship of China's new deep-sea manned submersible Fendouzhe (Striver), berths at a port in Sanya, south China's Hainan Province, Dec. 21, 2020. China's scientific research ship Tansuo-2 returned to port in the city of Sanya, south China's Hainan Province on Monday, after completing its ocean expedition. (Xinhua/Zhao Yingquan)

Crew members of Tansuo-2, the second mother ship of China's new deep-sea manned submersible Fendouzhe (Striver), receive flowers from people who are here to greet them in Sanya, south China's Hainan Province, Dec. 21, 2020. China's scientific research ship Tansuo-2 returned to port in the city of Sanya, south China's Hainan Province on Monday, after completing its ocean expedition. (Xinhua/Zhao Yingquan)

Crew members of Tansuo-2, the second mother ship of China's new deep-sea manned submersible Fendouzhe (Striver), disembark from the vessel with their relatives who are here to greet them in Sanya, south China's Hainan Province, Dec. 21, 2020. China's scientific research ship Tansuo-2 returned to port in the city of Sanya, south China's Hainan Province on Monday, after completing its ocean expedition. (Xinhua/Zhao Yingquan)