It is officially summertime and cruises to the Caribbean are going for some great rates. You can book a five-night cruise departing from Tampa or Fort Lauderdale for under $450 per person. All meals are included and the ships stop in places like the Keys, the Bahamas and Cozumel, Mexico. It seems unlikely that cruise ships could make any money with such affordable rates to tropical destinations. After all, it costs more money to stay at the Embassy Suites Downtown Tampa hotel on the same nights, and breakfast is the only meal included.

But once you board the ship, it all becomes clear: cruise liner companies have you marked as a cash cow, and rightfully so. Tasty rum drinks, professional photographs and expeditions are all very tempting and sell for a premium. Plus, you are there for a vacation; you shouldn’t have to worry about being frugal. You're there to relax and stuff your face from the dozens of eateries on board. You shouldn’t go for broke, though. Preparation can save you from crying on the drive home.

First off, figuring out the pesky business of drinking on board. Most ships have water, tea and juice for free, or you can purchase “soda cards” which allow for unlimited fountain drinks for a few bucks a day — a smart buy. But, for those serious about their drinking, which is generally a fair amount of the cruisers, the bar tab can easily go past the amount you spend on your room.

This article appears in Jun 10-16, 2010.