-- Last Updated: Oct-13-10 11:45 PM EST --
...... sunning on rocks , tree limbs at the water's edge . Also on rocks that are in the water .
Like you , I have come across copperheads at the water environment probably about as many times . Then again , probably no more than that many times away from the water environment as well ... so that's about fifty-fifty for me .
Copperheads do swim in the water just as you have described ... to me that , and the finding them at the water debunks the theory that they are not aquatic .
Vipers are not difficult to positively identify as long as you can get a good look , they have very distinctive ID features that are unmistakable and not found on any other snakes ... color being the "least" of those features .