The reptilian thermostat, or lack thereof, which makes crocs seek desirable warm water and air temperature. They must have a warm environment the year round. Alligators are able to tolerate slightly colder waters.
Crocodiles cool themselves by holding their mouths open, just like panting dogs do.
Evaporation from the mouth can cool them off even while they lie in the sun for hours. These hollows in the mud can be as much as 65 feet in length. Gavials are the sole living member of the family Gavilalidae, and one of the largest extant crocodilians. Once near extinction, successful breeding programs have stabilized their population. It is like swimmers' goggles, crocodile style.