How does an alligator keep warm?

American Alligator. ©Teresa Shumaker

Saw this alligator while I was visiting the South Padre Island Birding Center the other morning. SPI has had an unusually cold winter and this morning the wind was blowing about 15 mph and the thermostat was hovering in the mid 40s.
Luckily, my time on the Mendocino Coast has hardened me toward cold weather (not extreme cold, though) and I won't let a cold windy day hold me back.

I was making my way through the boardwalk and as I came up to alligator alley, where this wild alligator hangs out. I noticed he (only a guess on gender) looked a bit odd.

I could only see his head, and with the clear water I should have seen the rest of his body.

Only a head? ©Teresa Shumaker

 Turns out, alligators will bury themselves in the mud to keep warm and that is what this gator had done.

On the left are bubbles from him moving his leg beneath the mud. ©Teresa Shumaker

©Teresa Shumaker

 At first, he didn''t mind my presence and I was able to stand on the boardwalk just above where his tail would be.
But, after a few moments, I noticed bubbles coming up as he was wriggling out of the mud. Knowing how cold it is and how nice it must be to be warm in the mud, I backed off and left him in peace.

Side story: I love alligators, or am terribly terrified of them... possibly both. Ever since I was little, I have had dreams at least once a week about alligators and crocodiles.
I can't accurately describe the dreams as nightmares, but they usually are not happy dreams, either.
Most of them revolve around me, wading in a body of water, realizing that there is an alligator (or many) in the water that is watching me.
The rest of my dream is a moderately frightened stare off, as I try to think of a way out of my predicament.
I imagine in real life I wouldn't be "moderately frightened."
Whether they are nightmares or not, those dreams have given me a lifelong fascination of these beautiful creatures. I'm thrilled I get to see them in the wild!