White sand
Compostela
Spain · sea 17.1 °C at its warmest, in August

Sea temperature month by month
Monthly means in °C, NOAA OISST v2.1 climatology 1991–2020, sampled 27 km offshore, at the nearest open water cell of a 0.25° grid.
About
La Playa de Compostela es una playa de la localidad de Carril, en el municipio de Villagarcía de Arosa (provincia de Pontevedra, Galicia, España).
Questions
How warm is the sea at Compostela?
The sea off Compostela averages 17.1 °C at its warmest, in August, and 13.2 °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 Compostela?
The sea here never averages 20 °C in any month, so swimming means cold water all year. Some people do it anyway.
Where is Compostela?
Compostela is on the coast of Spain, at 42.6076, -8.7687. The map on this site flies straight to it.