Cruises are among the most popular romantic vacations for Americans. In fact, couples account for more than 79 percent of all cruisers who typically go for six or more days, spending an average of $1,690, not including airfare, according to Cruise Lines International Association.

That "sweetheart" deal can turn sour, however, if couples do not research and prepare to make sure everything goes smoothly at sea. Travel insurance is a good way to avoid common travel problems, according to one expert.

"In the 16 years I've been cruising, I've seen many people fall ill and be taken off the ship in port or even evacuated at sea by helicopter," said travel writer Anita Dunham-Potter. "All cruise vacationers should buy travel insurance."

Be careful though--some plans are better than others. Cruise lines usually sell insurance but it is often restrictive, only covering the cruise itself, not delays due to missed connections, or additional expenses for flights, shore excursions, and accidents or illness that happen off of the ship.

And cruise lines can't cover themselves, so if the cruise company goes out of business, travelers will lose their trip and their money.

On the other hand, a third-party travel insurer can reimburse for the entire cost of the trip and offer a wide range of life-saving and cost-effective benefits. For example, Access America, a leading travel insurance provider, said few people can afford medical evacuations.

"Medical evacuations can cost more than $100,000 and must be paid up-front," said Beth Godlin of Access America. The company recommends considering plans with coverage for:

• Missed connections

• Flights and shore excursions

• Supplier default or bankruptcy

• Lost or delayed baggage

• Medical assistance, including emergency evacuations.

The price of insurance ranges from 4 to 8 percent of trip cost, depending on the type of plan and the traveler's age.