Beach
Salina de San Juan
La Guajira Department, Colombia · sea 28.6 °C at its warmest, in October

Sea temperature month by month
Monthly means in °C, NOAA OISST v2.1 climatology 1991–2020, sampled 16 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 Salina de San Juan?
The sea off Salina de San Juan averages 28.6 °C at its warmest, in October, and 24.5 °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 Salina de San Juan?
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 Salina de San Juan?
Salina de San Juan is on the coast of La Guajira Department, Colombia, at 11.7328, -72.5922. The map on this site flies straight to it.