This was the first time I had ever seen a bull alligator display.
They produce a very low frequency sound as they lower their back into the water.
When this occurs it causes water droplets to literally dance off their back and the water surface.
Their bellow is amazing to hear and reminds one of what dinosaurs must have sounded like.
Alligators are thought to have been on earth for the last 17 million years.

Corkscrew Swamp Sanctuary
Florida