The snapper was quite large--its shell was over a foot across--and it appeared to be quite old, at least 20 years or so was my guess. A look at the animal's front leg looks like it has had substantial experience.
I was able to determine that it was alive, as it generally kept moving to face me and my camera as I walked around trying to get shots.
Here is a front-on shot from just a few feet away.
I realize that turtles are slow, but on one occasion, at least, she(?) made a "sudden" movement toward me, encouraging me to keep my distance. She also opened her beak in the following shot.
Finally, a couple of closeups, the last of which clearly shows that the turtle has "whiskers," one on each side of her beak, curled and stained green (presumably from pond scum, or whatever). Who knew?