Aqua Identity

•  Though the Cottonmouth occurs throughout Florida, it is not as abundant as the many species of harmless watersnakes that occur in much the same habitats.
•  Many Florida residents do not even realize that watersnakes exist. As a consequence, every large dark-colored snake found near water is counted, and usually killed, as a Cottonmouth. There really is no excuse for this because Cottonmouths can easily be distinguished from Water Snakes.
• If the head is viewed from above, the eyes of cottonmouths cannot be seen while the eyes of Water Snakes are visible;
• Cottonmouths have elliptical pupils and Water Snakes have round pupils;
• Cottonmouths have a facial pit between the nostril and the eye, and Water Snakes have none.
• Brightly-colored baby Cottonmouths are sometimes mistaken for the Southern Copperhead (Agkistrodon contortrix), which occurs in Florida only in the panhandle. The two species are easy to distinguish because the dark bars on juvenile cottonmouths have numerous dark spots and speckles in them, while the dark bars on the copperhead have no dark spots or at most only one. In additioin, the eye of the copperhead is not obscured by the dark facial band typical of the cottonmouth.

 

A. Top of the head (notice the large plate-like scales on the top of the head, and that the eyes cannot be seen from above)
B. Underside of the head (chin and throat)
C. Front (face view) of the head
D. Side of the head (notice the facial pit between the eye and the nostril)
E. Keeled Scales
F. Elongated scales below the tail (subcaudal scales) are typically undivided

Copied from Florida Museum of Natural History: http://www.flmnh.ufl.edu/herpetology/fl-guide/agkistrodonpconanti.htm