Ok, bored on a train to Helsinki, so a few thoughts:
1) From what we can tell, the lagoon at the waterfall has had 3 cases in it: The marshall's gun case, Hurley's (Charlie's?) guitar case, and Hurley, a HEAD CASE. Sorry. 2) A precedent for an inland boat. In the 1977 movie CLOSE ENCOUNTERS OF THE 3rd Kind, a very large commercial boat is found in the Gobi Desert, Mongolia, many thousands of miles from water, having disappeared 30 years earlier in the caribbean sea. That's all, carry on.