Beach
Plage de Porsliogan
Le Conquet, France · sea 16 °C at its warmest, in August

Sea temperature month by month
11Jan
10.4Feb
10.2Mar
11Apr
12.4May
14Jun
15.4Jul
16Aug
15.2Sep
14.5Oct
13.6Nov
12.3Dec
Monthly means in °C, NOAA OISST v2.1 climatology 1991–2020.
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 Plage de Porsliogan?
The sea off Plage de Porsliogan averages 16 °C at its warmest, in August, and 10.2 °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 Plage de Porsliogan?
The sea here never averages 20 °C in any month, so swimming means cold water all year. Some people do it anyway.
Where is Plage de Porsliogan?
Plage de Porsliogan is on the coast of Le Conquet, France, at 48.3475, -4.7704. The map on this site flies straight to it.