Beach
Praia do Forno
Rio de Janeiro, Brazil · sea 25.1 °C at its warmest, in March

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 Praia do Forno?
The sea off Praia do Forno averages 25.1 °C at its warmest, in March, and 21.3 °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 Praia do Forno?
The sea reaches 20 °C or more from All year. Twenty degrees is where most swimmers stop calling water cold; below it, a wetsuit helps.
Where is Praia do Forno?
Praia do Forno is on the coast of Rio de Janeiro, Brazil, at -22.9653, -42.0150. The map on this site flies straight to it.