Amerzone

Reasonability:
The challenges, such as they are, are fine, but the story poses some strange
questions:
*) Why are the white birds so significant? They look like just some
   semi-domesticated relative of the albatross.
*) Valembois had computer floppies in the 30's?!!! Compatible with his current
   version, too, although that's less surprising.
*) Sixty-odd years later and his wood and vine structures are still standing
   and operational in the heart of a jungle. Okay, except that the natives that
   might have maintained them have apparently deserted the place. Papers are
   still there where he left them -- in the open!
*) The old fisherman on the dock kept that key with him all this time! He could
   have, e.g., just told you it was in a drawer in the bar.
*) The hydrafloat is unrealistic, but it's a good bit of kitschy fun.

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Difficulty:
*) the initial direction to l'Amerzone -- The clue is strange, but clue it is.