Whether it's a silly upsell, like asking you to pay extra for fine dining on your "all-inclusive" vacation, or dumb laws that prevent you from boarding or disembarking, you won't fail to find something absurd at sea.

Cruise ships are unlike anything else in the travel industry. Maritime laws and ports of convenience ensure minimal regulations while cruise lines get to pocket the maximum profits.

Here are six practices that defy explanation, and how to get around them:

NONSENSE MARITIME LAWS

When James Dixon missed his cruise in Miami because of a flight delay, he tried to catch the ship in Key West, Fla. When he arrived, a cruise line representative informed him that because of the Jones Act, he and his party couldn't board. "I was in tears because our scheduled vacation for my mom was ruined," he says.

I asked my colleague, cruise expert Anita Potter, what was going on. "Yes, there is such as thing as the Jones Act — this law was designed in the 1800s to protect and regulate the American shipbuilding industry and ensure a fleet of United States-flagged ships," she told me. "In today's world this law is very outdated — and sadly, still in effect."

In Dixon's case, the Jones Act forbids foreign ships, which includes most major cruise line fleets, to transport cargo or passengers between two United States ports without first stopping at a foreign port.

THE RESTAURANT UPSELL

Most cruise ships offer "premium" dining that costs extra. If you want a 'special" restaurant experience, they say, why not go out for a steak dinner?

Frequent cruiser Candice Sabatini has a different take. "I've already paid $5,000 on an all-inclusive cruise," she says. "Also, I think it (implies) the cruise line will serve sub-standard food in the main dining room." That's why she avoids cruise ships that don't include all meals.

Some cruise lines are truly all-inclusive. You have to look long and hard — and sometimes you have to pay a lot more — to get them. But if you don't like being charged for something that should be included in your cruise, it's worth the effort.

NICKEL AND DIMING

More than the best restaurants cost extra. That margarita you ordered with lunch is $8. Sodas are extra, too. So are excursions, and pretty much anything else that isn't bolted down on the ship.

For example, Diane Hansen found that her luxury cruise didn't allow her to use the sauna and steam room without paying a surcharge. "We were going to get a couples massage on board," she says. "Instead, we opted for one on shore and didn't spend any money at all in the onboard spa."

AIR DEVIATION FEES

Most travel experts recommend booking your airline tickets when you buy a cruise, because you'll be more protected if you miss a connection. "But you have no idea what your flights are going to be, nor what they will cost," says Peter Mescher, a computer engineer from Raleigh, N.C. "When the cruise line reveals your itinerary, if you don't like it, you call them and pay an air deviation fee."

Even then, you don't necessarily get the flight you want, but instead choose from a basket of possible itineraries. You'd probably be better off buying the airline tickets yourself and finding a good vacation insurance policy that would help you if you had to cancel or get delayed.

THE CRUISE CONTRACT

Cruise contracts seem to be written by a team of maritime lawyers who want to take your money and give you nothing in return.

Think I'm kidding? Reader Melissa Aakre just returned from a cruise to Jamaica and the Cayman Islands. "On the first day at sea, we were told that the ship had a propulsion problem and that we were not going fast enough to get us to Jamaica, and that they were hoping we could get to Grand Cayman," she recalls. "On day three we were told we would only make it to Nassau, Bahamas, which is just 90 miles from Miami." What did she get for the missed ports? A $75 credit.

The cruise line should have refunded her port fees, but a review of her cruise contract — the legal agreement between her and her cruise line — shows it didn't owe her much more than that. It had no obligation to keep to the advertised schedule.

JEWELRY AND ART SALES

Smart cruisers stay away from onboard art auctions. Onboard jewelry seminars also should be avoided. "These events are tagged as educational seminars that also include tip sheets on where to buy while in port, and on some cruise lines includes a 'buyer's guarantee' that is supposed to help the passenger with refunds in the event that they are unhappy with the purchase," says Jacci Dewdney of Advanced Jewelry Appraisals in Des Moines. "What continues to amaze and frustrate me is that passengers either are not told, or do not understand, that the jewelry stores on the list have paid a premium to be listed, and are essentially paying the cruise line to funnel passengers to them."

Christopher Elliott is the ombudsman for National Geographic Traveler magazine. You can read more travel tips on his blog, elliott.org, or e-mail him at celliott@ngs.org.