Comment by Zenbit_UX
Cave diver here, the article asserts how rare warm caves are but I think that is a very European mindset.
The Mecca for cave diving is in the Yucatán and surrounding areas and the caves there are exceptionally warm. The surface water can be chilly, coming in around 21c at one of the many cenotes (sinkholes, which are the entry points into the system) as rainwater fills them, but the further into the cave you penetrate you will eventually cross the halocline, at which point deeper = warmer ocean water. It’s quite unintuitive but delightful to warm up after a 2+ hour dive. It’s common for divers to go deeper, pull their wetsuit open a little to fill it with warmer water (24c+) and then rise up back to the planned depth.
Cold cave diving is a very different experience and is usually found in Florida and Europe. Don’t recommend.
Recreational (not caves, no thank you!) diver here, jealous of your balmy 21C=70F water temps.
Here in lakes Michigan and Superior, diving on wrecks usually brings you below the thermocline to water temps from 0C to 10C ~= 50F. Only on rare inversions or at the surface at the south end of the lakes do water temps get much above 70.
You Florida, Carribean, and Central American divers have it made with your balmy water temperatures!