If you're planning a cruise, especially an exotic one, it's important to research whether you'll need a visa as soon as you book your trip. For example, there are many cruises that visit both Australia and New Zealand on one itinerary. While Australia requires a visa, New Zealand does not if you are staying for less than three months. If you are on a cruise in South America, you will need a visa to visit Brazilian ports, but not Argentinean. The Falkland Islands off the coast of Argentina also require a visa.
Cruisers to China need a visa to enter the country, and many countries in Southeast Asia also require visas. Cruisers traveling the Mekong or Irrawaddy need one for Cambodia, Laos, Vietnam, and Myanmar.
The Caribbean, the most popular cruising itinerary, does not require visas, with one exception: Cuba.