CNN analyzed the Carnival Cruise contract and concluded that despite 5 days of getting a lot less of what they bargained for (food, air conditioning), and a lot more of what they didn't want (open sewage), passengers were nonetheless "out of luck."
But a comment on the ContractsProf Blog says, maybe, not so fast. "Look at 45 N.E. 367. If maritime law applies,Carnival is subject to an innkeepers liability. The 5 day disclaimer may be against public policy and in contravention of the common law."