A spate of cruise ship difficulties of late — including Carnival's slow boat to Tampa, the seemingly lost at sea Carnival Triumph that stranded 3,100 folks in the Gulf of Mexico without electricity for days and the truly terrifying sinking of the Costa Concordia in Italy last year — raises concerns about the safety of taking a floating vacation, which 20.3 million are expected to do this year.

Two cruise ships in Turks and Caicos Islands. — Istockphoto

While the likelihood of a life-threatening event occurring while you are on board one of the 400 ocean liners cruising the world's waterways on any given day is actually tiny — in the past dozen years just 100 ships have gone adrift or otherwise jeopardized safety — it's prudent to understand the risks and be prepared.

From a passenger's perspective, the most relevant cruise ship problems can be narrowed down to two types: health issues and hassles.

Ross Klein, a sociologist in Newfoundland who meticulously tracks incidents on cruises at cruisejunkie.com, says, "Consumers should recognize that in the vast majority of cases, it's a matter of being inconvenienced, as opposed to being a threat to safety."

A few of the risks to consider:

Norovirus

If you just consider the statistics, you would think it unlikely that you will contract that terrible stomach virus. According to the Centers for Disease Control and Prevention, last year 2,791 passengers reported "symptoms of diarrheal disease," which is a tiny fraction of all passengers.

But cruisejunkie's Klein points out that there are far more cases than those included in the figures. The CDC only records the numbers of sick passengers if the cruise ship sails in or out of a U.S. port, and more than 3 percent of the ship's passengers have reported symptoms. Some passengers know that if they report gastrointestinal upset, they might be quarantined to their rooms — so plenty of people keep their sickness to themselves.

Of course you can catch norovirus on land as well.

What you can do: The most effective way to protect yourself, according to the CDC, is with good hygiene: That means thorough hand-washing with soap and water, not just using hand sanitizer. Also, after washing, use a towel to turn off the faucet, and then to open the door as you leave. (Good advice for when you're on dry land, too.)

Next page: Medical incidents and the fine print on your ticket. »