Champ might be a prehistoric reptile, a fish, or a mammal, living in Lake Champlain, or on the other hand it might be just a myth passed down through the centuries to amuse the masses.   P. T. Barnum once put up a $50,000 reward for the creature's hide.   Needless to say it was never collected.   Like all subjects of great controversy, there are always the hard-core believers, and the firm skeptics.