Craspedacusta sowerbiiis, a freshwater jellyfish, swims in Mengzi Lake in Zoucheng City, East China’s Shandong Province, June 3, 2017. The jellyfish is known to have existed for 550 million years and is of high research and aesthetic value. The species demands a high-quality living environment, so its existence in large numbers shows water quality in the city has improved significantly. (Photo/VCG)
