For everyone's information, the distribution of the cottonmouth in Tennessee only includes the western part of the state (mainly west of the Tennessee River) and potentially near the Alabama border. Cottonmouths are commonly mistaken for several species of water snakes. Anyone who claims to have encountered a cottonmouth in East Tennessee has misidentified another species (most likely a Northern Water snake or potentially a black rat snake). Water snakes can be heavy bodied and have coloration that could potentially be mistaken for that of a cottonmouth. Water snakes can also be fairly aggressive. However, once you have witnessed a cottonmouth up close and personal, you will quickly learn to distinguish them from other non-venomous species. One of the best diagnostic characteristics is the shape of the head. Cottonmouths (like that of other pit-vipers) have a triangular shaped head that is quite large. Many snakes will try to flatten their heads when threatened, however, look at a few photos and you will be able to see the difference.