Thick, heavy-bodied snake
Dark coloration, often brown, olive, or black
Distinctive broad, triangular head
Narrow neck behind the head
Vertical, cat-like pupils
Heat-sensing pits between the eyes and nostrils
Often shows a white mouth lining when threatened
Can have faint crossbands or blotches, especially in younger snakes
Keeled scales that give a rough appearance
Usually found near water such as swamps, marshes, ponds, and streams
Often floats with much of its body visible on the water surface
Tail tapers gradually rather than ending abruptly
Juveniles may have brighter patterning and a yellow-tipped tail
Defensive behavior may include coiling and gaping the mouth