Beach
Xialiao Beach
Wanli District, Taiwan · sea 28.4 °C at its warmest, in August

Sea temperature month by month
Monthly means in °C, NOAA OISST v2.1 climatology 1991–2020, sampled 18 km offshore, at the nearest open water cell of a 0.25° grid.
Wikipedia has no article about this beach yet. It is on the atlas from its Wikidata record and its photograph.
Questions
How warm is the sea at Xialiao Beach?
The sea off Xialiao Beach averages 28.4 °C at its warmest, in August, and 18.9 °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 Xialiao Beach?
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 Xialiao Beach?
Xialiao Beach is on the coast of Wanli District, Taiwan, at 25.2183, 121.6520. The map on this site flies straight to it.