I found this beautiful cottonmouth/water moccasin (Agkistrodon piscivorus) yesterday and carefully captured some closeups of the little pit viper after moving it off of a busy walkway.
Cottonmouths, though they are venomous, have an undeserved bad reputation. In reality they are fairly docile animals. The second photo here shows their typical defensive display and the reasoning for their name, "cottonmouth". They will also rattle their tail much like a rattlesnake, but they lack an actual rattle. However, if they are on dry leaves, it can sound like a small rattle. I often hear people say that they've been chased by one of these, but I guarantee those stories are a dramatic embellishment. These snakes will sit still with this posture until they perceive a chance to escape and will quickly move away.
Unfortunately many people kill these snakes when they see them because they decide they are a danger to have around. Basically people kill them just for existing near them despite the snakes undoubtedly minding their own business. The irony is that most people that get bit by them are envenomated when they approach the snake in an attempt try to kill it. ¯\_(ツ)_/¯