Beach
Plage de la Boirie
Saint-Denis-d'Oléron, France · sea 20 °C at its warmest, in August

Sea temperature month by month
Monthly means in °C, NOAA OISST v2.1 climatology 1991–2020.
About
beach in Saint-Denis-d'Oléron, France
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 la Boirie?
The sea off Plage de la Boirie averages 20 °C at its warmest, in August, and 9.6 °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 la Boirie?
The sea reaches 20 °C or more from August. Twenty degrees is where most swimmers stop calling water cold; below it, a wetsuit helps.
Where is Plage de la Boirie?
Plage de la Boirie is on the coast of Saint-Denis-d'Oléron, France, at 46.0333, -1.3718. The map on this site flies straight to it.