When Holland America's Maasdam sets sail to the Caribbean in February, the first thing most of the 1,250 passengers will do is shed their clothes. Every stitch.
And why not? They will be participating in a nudist cruise -- just one of many special-interest sailings that cater to fans of everything from Star Trek to chocolate concoctions to the sound of Sinatra. The people who organize such cruises, sometimes chartering an entire ship, say they are a wonderful way for people with similar interests or lifestyles to get together.
Take the clothing-optional cruises. Nancy Tiemann, president and co-owner of Bare Necessities Tour & Travel, says that ``going to sea and nudity is a perfect match." Participants feel a level of comfort they sometimes can't find on land: Because the ship is filled with only nudist passengers, there is no snickering and no sitting by the pool in a soggy bathing suit . Passengers, however, are required to dress when the ship is in port -- one reason , Tiemann says , ``we like those days at sea" -- and in the formal dining room, although what they wear tends to be more informal than on traditional cruises.
How popular is nude cruising? In addition to the 10-night Hidden Jewels of the Caribbean sailing, which leaves from Fort Lauderdale on Feb. 3, three more such cruises are planned next year, some on ships larger than the Maasdam. No matter: ``Whatever the ship's capacity is, that's what we usually sell," says Tiemann.
Another popularly themed cruise with multiple sailings centers on Christianity. ``Passengers find a family -friendly environment that enriches their religious experience," says Honnie Korngold, president of Christian Travel Finder, which has five Christian-themed cruises coming up this year and next. One of the most popular is Cruise with a Cause, sailing from Port Canaveral, Fla., to Nassau and Coco Cay, Bahamas, June 4-8 aboard Royal Caribbean's Sovereign of the Seas. ``We had 2,300 participants last year," says Korngold, ``and this year we are expecting 2,600."
Passengers keep on the sunny side with Christian music, talks by leading evangelists, special events for children, and mission work ashore. But one of the biggest attractions is what isn't there. Unlike most cruises, no alcohol is served aboard and the casinos are shut tight.
Music of all kinds plays a part in many cruises, but it is the reason for a few. Two music-themed cruises, in fact, have strong Boston connections.
One is the seven-night Sinatra Tribute Cruise, hosted by Boston radio personality Ron Della Chiesa, and departing March 18 from Fort Lauderdale for a week in the western Caribbean aboard the Costa Mediterranea -- fittingly, an Italian ship.
Della Chiesa's mellow voice has been heard Saturday nights on WPLM -FM 's ``Strictly Sinatra" for a decade. Among his listeners are Dan and June Weiner, who run Galaxsea Cruises and Tours in Ashland and decided there could be no better host for such a sailing.
Says Della Chiesa: ``Sinatra was such an icon and he left such a legacy" that people from their 30s to their 70s are turned on by the man and his music. Of all the tribute singers who could have been welcomed aboard, Della Chiesa chose Steve Marvin, considering him simply the best. In addition, there will be talks about Sinatra, trivia contests, and, as Della Chiesa puts it, ``reminiscing and tall stories" about the powerful and sometimes politically incorrect ``Chairman of the Board." Another attraction will be Della Chiesa himself because many people who have listened to him for years want to put a face to the voice.
The Sinatra Tribute will be a cruise within a cruise in that most of the special events will be only for passengers who book through Galaxsea, and more than 100 are expected to do so. All of the ship's general events for the other 2,000 or so passengers will, of course, be open to the Sinatra seagoers.
The same holds true for those who remain lost in the '50s and book passage aboard the Norwegian Majesty for Harvey Robbins's 16th Annual Doo-Wopp & Rock 'n' Roll Boston to Bermuda Cruise, May 20-27 . Some 150 of the ship's 1,460 passengers are expected to book through Robbins for admittance into the concerts, games, and contests.
There are always several doo-wopp stars aboard. Eugene Pitt of the Jive Five has signed on and other possibilities are Shirley Reeves of the Shirelles and Earl Carroll of the Cadillacs. In addition, Robbins's Royalty of Rock and Roll All-Stars will be onboard. Robbins's energetic showmanship is a drawing card, too. Just ask Bob Kelley of Salisbury, who with his wife , Rose , has taken the cruise six years straight. ``Ya gotta love Harvey," he says. ``He's doing what he loves and it shows."
Music has been called the food of love, but lovers of food want the real thing. Food and wine events at sea are hardly a novelty -- unless, perhaps, the food in question is chocolate.
On Dec. 11, the Regent Seven Seas Navigator will embark from Fort Lauderdale on a weeklong Caribbean cruise that showcases chocolate and other favorite desserts. Christophe Michalak, head pastry chef at the Hotel Plaza Athénée Paris , will treat dinner guests to the dessert that won him a gold medal at the 2005 Pastry World Cup along with three other signature desserts during the cruise. He will also show how to make some of his favorite treats during two cooking demonstrations. And for those who like to drink their dessert, Thierry Hernandez, director of the Bar du Plaza Athénée, will concoct such tasty-sounding libations as martini lollies and jellied cosmopolitans.
For those with alternative lifestyles, a cruise can be a breakthrough experience. A gay cruise, for instance, ``is especially helpful to people from small towns in getting to know people who share their lifestyle," says Diane Berube, travel service manager of Gay Days Travel, which books cabins on cruises for the general public and holds special events for the 100 to 200 gays who typically come aboard. The agency's First ``Official " Women's Gay Days Cruise will be aboard the Carnival Sensation, a three-night trip leaving Port Canaveral Jan . 18 and heading to Nassau. In addition to entertainment, there will be gifts, goody bags, and get-togethers.
There are many more special-interest cruises, among them sailings geared to lovers of all things Irish, baseball fans, history buffs, antiques hunters, and those who devour dance, design, and literature. But here's one that's out of this world, sort of. Cruise Trek is putting together its 15th annual Star Trek cruise, visiting Australia and New Zealand aboard Holland America's Staatendam Nov. 4-18, 2007.
While details are incomplete, the past trips, which have attracted from 100 to 750 passengers, show there is a lot more to the cruises than just walking around in Spock ears. Actors from the legendary TV show are aboard, and there are TV-parody games such as Match Trek and Wheel of Trek, contests, and rituals known only to Star Trek fans. People do dress up in Trekkie costumes, says Charles Datin, president of Cruise Trek, but how many varies from year to year. Datin's interest in all things Trek is understandable since his father, Richard, built the original model of the Starship Enterprise for the show.
After the cruise, there is an Internet chat room, where participants discuss their adventures, friendships, even romances. The cruise may not beam them up, but it appears to leave them beaming.
Richard P. Carpenter can be contacted at carpenter@globe.com. 
