While collecting stream insects for some lab rearing I was doing, I ran into this water snake.  Of course, I immediately picked it up and, astonishingly, was not bitten.  After a futile attempt to calm the snake, I set him down and snapped a few pictures of its aggressive, flatten stance.  The scale across the snake’s eye is blueish, indicating that it will likely molt soon.  Indeed, a couple of days later, I caught the same snake (well, presumably the same one, given that it was under the same piece of bark), and it had a fresh, shinning layer of scales. Further, its aggressiveness was reduced the second time around, adding to evidence, at least in my experience, that snakes get kind of angry when they are close to molting.