Chuck, that looks like an average size cottonmouth, they usually average around 3 ft and any thing bigger than 4ft is big and rare. Usually when approached and cannot escapethe cottonmouth will throw open its mouth wide open revealing the white in its mouth, getting its name the cottonmouth. When born they are around 6 inches and are light brown/copper in colour and resemble a small copperhead, actually the copperhead and cottonmouth are very close relatives with a copperhead being called a highland moccasin and a cottonmouth called a low land moccasin. Both snakes venom pocessessimuliar characteristics, not a real potent hemo-toxin, but bad enough to reuin your week and possible amputation of an extremity. Be careful fishing in moccasin country as they are attracted to a stringer of fish.
I got bit by a cottonmoth down in fla. a while back on my left index finger which left me with a feelingless, deformed finger and had to go through a seris of skin grafts and scare tissue filled in the rest. Thats the reason I type so slow, so if it takes you a while to read this, you know why I'm so slow.

Bobby