Impossibilities of "Occurence at Owl Creek Bridge"

After falling about 20 feet off of a bridge into swiftly moving water, Peyton Farquhar is able to rise to the surface and there he is greeted by the "blinding sunlight." Yet, his physical senses manage to be "preternaturally keen and alert." This is proved when he is able to see in detail all of the action taking place on the bridge. He is able to see all the soldiers running about and a rifle's muzzle, from which he sees "a light cloud of blue smoke rising." Even more peculiar is the fact that he is able to determine the color of one of the sentinels, who had just shot his rifle and s…