Beach
Boca Chica State Park
Cameron County, United States · sea 28.9 °C at its warmest, in September

Sea temperature month by month
Monthly means in °C, NOAA OISST v2.1 climatology 1991–2020, sampled 14 km offshore, at the nearest open water cell of a 0.25° grid.
About
state park in Boca Chica Village, Texas, United States
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 Boca Chica State Park?
The sea off Boca Chica State Park averages 28.9 °C at its warmest, in September, and 18.7 °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 Boca Chica State Park?
The sea reaches 20 °C or more from April to December. Twenty degrees is where most swimmers stop calling water cold; below it, a wetsuit helps.
Where is Boca Chica State Park?
Boca Chica State Park is on the coast of Cameron County, United States, at 25.9969, -97.1517. The map on this site flies straight to it.