Cruise shopping is the first fun step of your cruise vacation, but it can be challenging to navigate all the details, not only when it comes to choosing your cabin and finding the ideal itinerary but reading all the fine print and knowing how it may affect your trip. We read (and read and reread) some of the fine print for you and came up with a list of the important things you might overlook as you prepare for your cruise.

1. Fees can change after you've paid in full.

When you read the terms and conditions, it becomes clear that on most cruises, the port fees you pay at booking are the cruise line's best guess of your individual share of what the ship will be charged for docking at the ports of call planned for the cruise. The caveat is that if those estimates change, you might owe more. A search of the Cruise Critic member boards turned up few cruisers who had been charged additional amounts after purchasing their cruise, but the cruise lines reserve the right to do so.

The same applies to fuel supplements. In the event of a dramatic increase in the cost of fuel, you may be charged a fuel surcharge, even after you have paid in full. Most cruise lines use a specific crude oil price as the point at which they might add the fuel surcharge. In recent years, most lines have opted to absorb these fuel fluctuations without adding the charge to customer's bills, but most cruise lines tacked on fuel surcharges during 2007 and 2008, with a few bringing them back in 2011.

2. You will be charged the penalties imposed under the PVSA if you disembark in the wrong port.

Often confused with the Jones Act, the PVSA is the law that prevents non-U.S.-flagged ships from transporting passengers between U.S. ports of call. It's a complicated law with lots of exceptions, but the important thing you need to know from the fine print is that if you depart the ship (and do not return) unexpectedly in most U.S. ports, you might be subject to the fines imposed on the ship for "transporting" you.

3. The cruise line has strict limits on what should not be in your checked bags.

One tends to assume that what cruise lines allow in checked bags would be roughly the same as what airlines allow, but that is not necessarily the case. Each cruise line has a list of things they consider dangerous or against policy to have inside checked luggage. The lists may include beer, wine or other alcoholic drinks; bottled water; knives (or scissors) of a certain length; and electrical devices or appliances that could pose fire hazards. This is one part of your cruise contract that is worth keeping handy as you pack to avoid luggage delays and confiscation on embarkation day.

In addition, the cruise lines reserve the right to search your luggage, your stateroom and even your safe if they determine you might be traveling with drugs or anything else banned by the cruise contract.

Travel insurance can help cover lost or damaged luggage

4. If your luggage and contents are expensive, you should buy travel insurance.

Each cruise line sets the amount they will be held liable for in the event of damage to or loss of your luggage, and it is likely to be less than you would expect. Many lines offer an option that allows you to provide proof of greater value, but they charge as much as 5 percent of the amount over their base limit to "insure" the bags and contents. Travel insurance is usually a better way to cover those potential losses.

5. You can't cruise after the 24th week of pregnancy.

This rule is standard across most cruise lines' terms and conditions. If you will reach the 24th week of pregnancy before the end of the cruise, you are asked not to book because you will not be allowed to board the ship. It would be wise to carry a doctor's note with you any time you are cruising with a baby bump to avoid any issues.

6. The age of your infant matters.

Most cruise lines will not allow infants under 6 months to cruise at all. The reason given is that the ship and many ports of call do not have adequate medical care facilities for very young infants. Longer cruises, expedition cruises and those traveling to remote areas often only allow children over 1 year of age.

7. Cruise lines get do-overs on fare mistakes.

Unlike airlines, in most cases, cruise lines do not honor tickets purchased on faulty fares due to website errors. Sorry, but if it looks too good to be true, don't count on the ticket being valid.

8. They can take you wherever they want and drop you off wherever they need.

The nature of travel on the ocean means that both the cruise line and the passengers must prepare for whatever comes their way. Ships may skip ports, change to alternate ports, change the departure and arrival schedules or detour in any way the company and the captain deem to be in the best interest of both ship and passengers. You will rarely be compensated for changes unless they are due to mechanical failure of the ship.

Along the same line, the ship does not have to take you to the port you expected to disembark in. You, personally, may be disembarked early for a variety of reasons, or the entire ship may be disembarked in an alternate port. When that happens, unless the change is due to mechanical failure of the ship, only passengers who booked air packages with the cruise line are likely to have assistance with re-booking transportation.

9. You might be kicked off for health reasons -- and charged for the privilege.

This may come as a big shock, but you may be denied boarding or removed from the cruise at any point if your health jeopardizes other passengers, or it is determined that the medical staff onboard cannot adequately care for you or assess the severity of your condition.

If you suffer a severe medical incident that requires the ship to make an emergency stop or call for assistance from a nearby port, not only is your cruise about to be cut short, but expect to pay for all that extra attention, including extra port fees and services.

10. You should sniff your sea shells.

Amid all the serious rules in the FAQ's and cruise contracts, we found a funny rule from Carnival, allowing you to bring shells onboard from ports, if they do not contain creatures (living or dead) and do not have a noxious odor.

11. Some cruises allow you to bring water and wine; others not so much.

We are guessing that the most-read section of most cruise contracts is the part about which beverages may be brought onboard. Many allow two bottles of wine per stateroom, with some restrictions regarding its consumption. Some allow bottled water, others only cartons or cans in limited quantity. River cruises and premium or luxury lines are the most nonchalant about beverages, but it is always wise to read the details of what is allowed on your specific cruise.

Man using tablet

12. The Wi-Fi is not private.

You know this, right? Even with a login, your private information is not secure on the onboard Wi-Fi. Cruise lines also reserve the right to snoop through your messages if they suspect you of nefarious activities. You sign that right over to them with the purchase of the cruise.

13. Not everybody you encounter during your cruise works for the cruise line.

It is always worth noting that certain people you encounter, both onboard and off, might not be employees of the cruise line itself. Tour guides and staff, port security and shoreside entertainers are the obvious non-employees, but even the onboard casino and spa may be operated by a private company. Your interactions with them are not the responsibility of the cruise line.

14. There are strict time limits for you to file grievances.

When things go wrong on a cruise, as they sometimes do, you have a very narrow window of time to file a grievance with the cruise line. In the event you plan to file legal action, the cruise contract will usually have timeline restrictions on both advance notification of those intentions, and the actual filing of the suit.

15. Cruise lines can prohibit you from taking video or photographs -- even of yourself.

Once you step onboard a cruise ship, you give up some rights. You are in a floating place of business and that business has the right to restrict your photography onboard. In most cases, enforcement is likely limited to use of the ship's photography studio props or entertainment venues, but if crew members ask you not to photograph something, be clear that they have the right to do so.

They can also make you take down your social media posts if they want. If the photos you posted online do not present the cruise line in a positive light, you can be legally compelled to remove them if you do not have prior written permission from the cruise line for the photography.

16. Deck chairs are not to be reserved.

It's in there, people. Check the fine print. Deck chair hogging is prohibited -- though randomly enforced according to Cruise Critic members on the 258 threads on the message boards containing the words "Chair Hogs" in their title.