Xuelong 2, or Snow Dragon 2, China's first domestically built polar icebreaker, moors at a port in Shanghai for a Maritime Day theme activity on July 11, 2020. July 11 marks the Maritime Day of China. (Xinhua/Zhang Jiansong)

Xuelong 2, or Snow Dragon 2, China's first domestically built polar icebreaker, moors at a port in Shanghai for a Maritime Day theme activity on July 11, 2020. July 11 marks the Maritime Day of China. (Xinhua/Zhang Jiansong)

Xuelong 2, or Snow Dragon 2, China's first domestically built polar icebreaker, moors at a port in Shanghai for a Maritime Day theme activity on July 11, 2020. July 11 marks the Maritime Day of China. (Xinhua/Zhang Jiansong)

Xuelong 2, or Snow Dragon 2, China's first domestically built polar icebreaker, moors at a port in Shanghai for a Maritime Day theme activity on July 11, 2020. July 11 marks the Maritime Day of China. (Xinhua/Zhang Jiansong)

People pose for photos against the background of Xuelong 2, or Snow Dragon 2, China's first domestically built polar icebreaker, which moors at a port in Shanghai for a Maritime Day theme activity on July 11, 2020. July 11 marks the Maritime Day of China. (Xinhua/Zhang Jiansong)