Not to pick on anyone here, as my experience shows that most of the people who post are informed sportsmen and are familiar with the outdoors. However, I believe most of the "sightings" of posionous snakes are actually harmless common non-venom snakes. I have friends that I fish the park with and they are always telling me about the copperhead or rattlesnake they saw, and if I go to the area and actually find it, the snake is never what they think it is.
In my experience the parks venomous snakes are not usually found along the streams where most of us spend our time. (There are exceptions, of course).
The northern water snake seems to get the most credit for being a posionous snake, and they are prob the most plentiful large snake that most anglers run into.
I would like to see what the rest of you think.