One fee that will surely catch some passengers by surprise comes up when buying drink packages.
A typical drink package will allow passengers to drink their fill for a fixed price per day. However, most cruise lines make every adult in the cabin buy the package, even if they don't drink.
"This is to keep passengers from sharing the package, but it often means there's an extra fee of an additional drink package for many couples traveling together," Tanner Callais, founder and editor of Cruzely.com, told Business Insider. "The good news is that cruise lines will sometimes work with you on the extra package, especially if there is some circumstance like being pregnant or a health issue that means the other person can't or won't drink alcohol."
There are also unexpected gratuity fees, even on free food or drink by the cruise line. For instance, some cruise lines offer perks where if you book the cruise, you can select perks like free drinks or free specialty restaurants.
"What's in the fine print is that even if you aren't charged for these items, you will be charged the gratuity of their original cost," Callais said.
Take a drink package that costs $100 per day. A 20% automatic gratuity is still charged, even if the package is free. In other words, on a week-long cruise those free drinks would cost the passenger $140.
"Be sure to read the fine print on any free perk offer from the cruise lines," Callais recommends. "If you don't like the overall deal, you can often skip the perks altogether and save the extra cash."