Babies are brightly banded and blotched in shades of golden brown and tan with bright yellow tail tips. They are often mistaken at this age for copperheads, a related species that is not found in Florida south of Liberty County. Adults tend to darken with age and may end up solid black, greenish or dark brown with very few visible markings. Both adults and babies have a "raccoon mask", a streak of dark brown bordered by white on the side of the face. Heads are heavy and triangular and pupils are elliptical. Their scales are dull and slightly rough in appearance, not shiny. Their bodies are thick, squat and heavy with a triangular profile, high narrow backbone and wide belly. Animals that feel threatened may coil tightly and open their mouths, showing a white "cotton mouth".

Lookalikes include several types of water snakes and black racers, which are often reported as cottonmouths. Urban legends about "nests full of cottonmouths" don’t jibe with their solitary habits. If you hear a report of a "whole nest of cottonmouths" clustered in one place, they’re actually water snakes.

Cottonmouths are one of the easiest venomous species to handle with hook or tongs. They have a reputation for being aggressive, but zookeepers and snake experts consider them docile and slow moving. They are often unafraid and very curious. Cottonmouths can be safely captured using a broom or mop and a tipped-over garbage can - here's how.

A cottonmouth bite can be serious, though unlikely to cause human fatality. Immediate hospital treatment is warranted. Clinical trials of the new CroFab antivenom seem extremely promising for cottonmouth bite.