Crocodiles are cold blooded. This means they get the warmth that their body needs from the environment. They cannot generate body heat by shivering, or cool off by sweating. So, how do they get the heat they need?
The main method that crocodiles get the warmth necessary for their bodies is by basking in the sun. As their bodies warm up, they open their mouths to cool off by evaporative cooling. The membranes in their mouths play a major role in regulating their body temperature. If the temperature continues to rise, some species will seek the shade, or return to the water to cool off. They also love to wallow in the mud, and these mud baths provide a means to regulate the body temperature too.
Crocodiles also regulate the amount of heat that they receive by placing just the tip of their nose or one leg in the sun. Another method is to remain partly submerged while basking in the sunlight. When the temperature drops, crocodiles become more lethargic. If there is a cold spell, the animal will completely submerge itself in deeper water where the temperature is warmer, and breathe through holes in the ice.