Hainan

Hainan is China's tropical island province, sitting in the South China Sea south of Guangdong. The tidal regime is mixed semidiurnal with spring ranges of 1.5–2.0 m — moderate, but enough to expose significant sand and reef flat areas on low tides. The island's south coast around Sanya has the clearest water in China and has been developed as the country's main domestic beach resort. Typhoon season runs June through September and can close coastal access entirely. The north coast faces the Qiongzhou Strait and the ferry corridor to the mainland. The Sanya National Coral Reef Nature Reserve protects fringing reefs accessible by snorkel and dive at Luhuitou and Wuzhizhou Island. Sea surface temperature holds above 25°C year-round, making Hainan the only part of China suitable for tropical marine activity in winter. Green and hawksbill turtles nest on the Wenchang coast in autumn; the nesting beaches are under government protection.