Alos, hate to overanalyze, but it is clear that Jack wasn't hallucinating and that when he was near the fire, he heard and saw soemthing close by that led him to that waterfall. It sounded like the clinking of ice in a glass. Like when his dad lectured him. That was an eerie scene as a whole. Sorry for so much off topic, but this show is fascinating. I hope they don't mess it up.
-------------
Go Bills