As cruise lines offer an increasing variety of themed sailings and shipboard activities, more travelers are choosing to combine the vacation fun of a cruise with a theme that pleases their palates: wine cruises.

On a wine-themed cruise, participants get to taste many different wines, learn about them from winemakers and wine experts brought on board, drink wines paired with special meals, and visit wineries and vineyards ashore. Such cruises have been around for a couple of decades, but they’ve really picked up steam in recent years.

“Wine cruises have increased a thousandfold,” said Larry Martin, CEO of Food and Wine Trails, a pioneer company in packaging wine cruises that annually books about 1,000 guests on 15 to 20 wine sailings. Expedia Cruise Ship Centers, another travel agency, started offering wine cruises three years ago and now does six to eight a year, said owner Brian Murphy.

Cruise lines also are ramping up their offerings. AmaWaterways, which operates 11 cruise ships on European rivers, scheduled eight wine cruises this year but will double that number in 2013. Celebrity Cruises has initiated a series of seven new “immersive European Wine Cruises” this fall to coincide with the harvest season.

Avalon Waterways started wine cruises in 2006. “They took a while to catch on, but they’re really popular now,” said the line’s Jennifer Halboth.

And the trend is not just limited to wine travel specialists and cruise lines. Major retailer Costco, which has a travel arm, is now offering wine cruises, with two still ahead this year and six planned in 2013.

What’s the appeal of wine cruises?

For wine lovers, it’s the combination of having access to wine experts and uncommon wines with the pleasures of cruise travel and interesting destinations.

“The best experience was tasting so many different wines,” said Julie del Rico of Delray Beach, who went on a Food and Wine Trails wine cruise on Oceania Cruises last year. She said the group enjoyed a lot of tastings in Italy and visited different vineyards ashore. “We also had tastings in Slovenia and Croatia,” she added.

Michael MacDonald, who went with his wife Debbie on an Avalon Waterways cruise on the Rhine and Moselle Rivers last year, echoed del Rico’s sentiment that tasting different wines was a highlight. “I like Reislings, but I didn’t realize there were so many varieties,” said the Connecticut resident.

Most wine cruises are not organized or conducted by the cruise line itself, but by a group that makes all the arrangements for wine lectures, tastings, pairings, special visits to wineries ashore and other wine-related functions, and charges a fee in addition to the cruise fare for the wine package. Of course, only those who have paid the fee can attend these functions.

Food and Wine Trails, for instance, charges $300 to $400 above the cruise cost for those participating in the wine events, said Martin.

Some cruise lines do put together true wine cruises, and those may be open to all passengers at no extra cost. “Our wine cruises are open to all on board our ships, not just a private group,” said Rudi Schreiner, founder and CEO of AmaWaterways.

On the other hand, some sailings that are labeled “wine cruises” or “food and wine cruises” may offer tastings and pairings but may not go in much depth as far as wine education. Before booking a wine cruise, prospective passengers should find out exactly what wine-related events are scheduled.