Half Moon Cay -- the private island in the Bahamas that Carnival and Holland America share -- looks like a movie set of a beach. The sand is pristinely white, with nary a scratchy shell or untoward piece of seaweed. The sea is warm, but not too warm, and turquoise, just like all the postcards you see of Caribbean beaches that you always assumed were fake. The cabanas are painted in bright, happy colors, and the bars have quaint thatched roofs and inviting Adirondack chairs -- or are set inside a faux pirate ship. You have to try to have a bad time there.