By Mark Cantrell

Cruising is one of the most popular vacations in the world, with some 24 million people choosing an ocean voyage in 2015. That's not surprising; a cruise ship serves not only as your hotel, but also your transportation, taking you to a new and exciting port of call every day or two.

There's something about being on the open sea that makes you want to kick back, forget all your cares and completely relax. After all, you've saved up for your vacation and have been looking forward to it for a long time.

While it's true you're there to have fun, you can run into problems on cruises just as you can on land. These nine tips can help ensure your safety while on board.   

1) Pay attention during the muster drill. Even if you've taken a cruise vacation before, a refresher on what to do if the ship encounters problems is a good idea. If you're a first-time cruiser, it's vital.

2) It's also important to maintain situational awareness, on or off the ship. Letting your guard down while aboard is a natural tendency, but bad actors aren't confined to land. Don't accept drinks from strangers, don't carry large amounts of cash, and keep away from dark hallways.

3) With no responsibilities and your captain as designated driver, it's easy to overdo it on the booze. But not only can alcohol compromise your judgment and lead to bad decisions, you don't want to waste your vacation leaning over a railing.

4) Speaking of railings: Be careful on your balcony; people can and do fall overboard.

5) If there's anything that can ruin a cruise, it's illness, and seasickness is near the top of the list for some travelers. To avoid it, the Centers for Disease Control recommends talking to your doctor and obtaining medication before you embark. Choosing an outside cabin amidships also can help limit the rolling movement that can exacerbate queasiness.

6) The CDC also suggests making sure your routine vaccinations, including a seasonal flu shot, are current before you cruise. Additional inoculations depend on which countries you're visiting; you can find a list of recommended vaccines by country at the CDC's Traveler's Health site.

7) Unfortunately, there is as yet no vaccine for the dreaded norovirus, which can spread through a cruise ship like wildfire and lay passengers low with vomiting and diarrhea that can last for days. Frequent handwashing with soap and water is one of the few preventive measures; alcohol-based hand sanitizer is slightly less effective but still recommended. Cruise ships are required to file a report if more than 2 percent of passengers are afflicted; the CDC maintains a list of outbreaks.

8) Research prospective shore excursions before you book that sightseeing tour or parasailing trip. Use Google or a site such as CruiseBruise. Cruise companies are obligated to warn passengers of possible dangers on shore; ask your cruise director or excursion manager about them before disembarking.

9) Not all ports of call are created equal. Check for State Department Warnings and Alerts for the destinations on your cruise itinerary.