Beach
Holiday Beach, Hainan
People's Republic of China · sea 28.5 °C at its warmest, in July

Sea temperature month by month
Monthly means in °C, NOAA OISST v2.1 climatology 1991–2020.
About
Holiday Beach (Chinese: 假日海滩) (officially Holiday Beachside Resort) is beach and visitor attraction located along Binhai Road, Haikou, Hainan, China.
Questions
How warm is the sea at Holiday Beach, Hainan?
The sea off Holiday Beach, Hainan averages 28.5 °C at its warmest, in July, and 19.3 °C at its coolest. These are monthly means from NOAA's OISST v2.1 satellite and buoy record for 1991 to 2020, sampled at the beach's own coordinates.
When can you swim at Holiday Beach, Hainan?
The sea reaches 20 °C or more from March to December. Twenty degrees is where most swimmers stop calling water cold; below it, a wetsuit helps.
Where is Holiday Beach, Hainan?
Holiday Beach, Hainan is on the coast of People's Republic of China, at 20.0792, 110.3892. The map on this site flies straight to it.