Sometimes, cruise lines ban things because they're dangerous. For obvious reasons you can't bring explosives, weapons, firearms and many other potentially scary items on board. You may want to go hunting when you reach your destination, but guns aren't allowed under any circumstances.

Hiding tiny rubber ducks has become a popular practice on cruise ships. Despite calls to ban it, Carnival hasn't. Their brand is tied to "fun," and ducks align with that.

Virtually every transportation company of any kind – including airlines, railroad, and cruise lines – have lists of items you are not allowed to bring with you. And while most Americans who travel are well aware of what you can’t take on an airplane,