Cottonmouth (Water Moccasin)
Agkistrodon piscivorus · Viperidae (Pit Viper)
Also called: Water Moccasin, Gaper
A semi-aquatic pit viper named for the white interior of its mouth, which it gapes as a warning. The only venomous water snake in North America.
What the Cottonmouth (Water Moccasin) looks like
How to identify it
- 1Thick, blocky body and a flat-topped, angular head
- 2Gapes open to flash a cotton-white mouth lining when threatened
- 3Dark olive, brown or near-black with faint bands
- 4Swims with most of its body riding on the water surface
Snakes it's confused with
Harmless; slimmer head, swims low in water, no white gape.
Behavior & danger to humans
Stands its ground and gapes rather than fleeing. Bites deliver potent tissue-destroying venom.
⚠️ Danger: Serious bite that can cause severe tissue damage. Seek emergency care immediately.
Related snakes
VenomousEastern Diamondback Rattlesnake
Crotalus adamanteus
The largest venomous snake in North America and arguably the most dangerous. Its hemotoxic venom destroys tissue and blood cells, and a defensive bite is a medical emergency.
VenomousCopperhead
Agkistrodon contortrix
Responsible for more venomous snakebites than any other US species, but its bite is rarely fatal. Excellent camouflage in leaf litter leads to surprise encounters.
VenomousEastern Coral Snake
Micrurus fulvius
A relative of cobras with potent neurotoxic venom. Famous for the rhyme 'red touches yellow, kill a fellow' that separates it from harmless mimics.
VenomousWestern Diamondback Rattlesnake
Crotalus atrox
The classic Western rattlesnake responsible for the most snakebite deaths in the US. Recognizable by the black-and-white 'coon tail' banding above the rattle.