Do fish sleep? How do sea creatures spend the night? The answers could be found in special programs organized by Nanjing Underwater World in east China’s Jiangsu Province during the summer vacation. /CFP Photo

A group of children spent a night in the underwater tunnel at the aquarium on June 24, 2017, with sea creatures swimming overhead. /CFP Photo

Museums and aquariums in China rarely offer night programs. Nanjing Underwater World started offering such a unique experience in 2015. /CFP Photo

With a long coastline that ranges from temperate to tropical oceans, China has some 3,000 marine species. The country has carried out a series of projects for marine ecosystem conservation, pouring in 11 billion yuan (about 1.6 billion US dollars) since 2010. /CFP Photo