The sad fact of the matter is, no matter what any park puts on a ticket or a sign at the entrance to a ride patrons can (and do) sue for all sorts of things, including injuries that are a direct result of their own behavior. To wit - Knott's Berry Farm last year settled a lawsuit with a woman who sued over a broken leg she suffered while on their rapids ride. How did this occur? Despite all the signs that warned "You will get wet on this ride" she decided after boarding she did not want to get wet. As the raft approached a waterfall she unfastened her seat belt AND JUMPED OUT, breaking her leg. Knott's lawyers advised the settlement because they felt she would most likely win at trial. This is a particularly extreme (and offensive) example, but it's a wonder, given the litigious climate out there, that parks open rides with any thrills at all.
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Age and treachery will always overcome youth and skill.