Some of the headlines about cruising have been downright frightening. Whole ships full of people being quarantined to their cabins with serious stomach flu? An unpleasant end to a much-anticipated vacation. Pirates commandeering one of the more luxurious ships on the water? That's the stuff that nightmares are made of. But the reality is that you're much more likely to suffer from a sunburn or a hangover on a cruise than anything more serious. Here are the most worrisome horrors at sea, and why they're just not that likely.