Children cool off in the sea in Sanya City, south China's Hainan Province, July 3, 2018. (Xinhua/Chen Wenwu)

Tourists drift on water at the Tianqiaoyu scenic spot in Chengde City, north China's Hebei Province, July 4, 2018. (Xinhua/Wang Liqun)

Tourists drift on water at the Tianqiaoyu scenic spot in Chengde City, north China's Hebei Province, July 4, 2018. (Xinhua/Wang Liqun)

Tourists drift on water at the Tianqiaoyu scenic spot in Chengde City, north China's Hebei Province, July 4, 2018. (Xinhua/Wang Liqun)