natgeo Video by @melissalesh and @tbfrost | TURN ON SOUND! | A juvenile cottonmouth (also known as a water moccasin) snake slowly moves across a shallow pool of water while on the hunt for frogs in False Cape State Park, Virginia. Cottonmouths are venomous and are quite common in the southeastern United States, though you don’t find them north of the Appomattox River in Virginia. The name cottonmouth comes from the bright white mouth they have (it resembles a ball of cotton), which they readily flash at anything that threatens them, including humans. Cottonmouths have a reputation as being aggressive snakes but that isn’t the truth, they just stand their ground, meaning once threatened they tend to freeze, flash open their mouth, and rattle their tail eventhough they don’t have actual rattles.