Have you ever wanted to meet a favorite music legend after a concert, sip a fine glass of Pinot Noir poured by an award-winning winemaker, play poker with tournament champs, dance to polka bands every night or don an apron to cook alongside a celebrity chef?

Then you might want to consider a theme cruise vacation. Theme cruises -- sailings focusing on a hobby, area of interest or celebrity, as well as floating music festivals -- can be a backstage all-access pass to your passions.

They're increasingly popular, and it's easy to see why. Themed sailings offer immersion in a favorite activity or interest, combined with all the resort-like amenities of a cruise ship and the excitement of traveling to new places. They can include meet-and-greets with famous people, a lecture series, concerts, hands-on activities, days of dance lessons, classroom sessions or special-focus guided excursions while in port. You can indulge in your favorite pastimes, learn a new skill and make friends with like-minded people.

Theme cruises enable you to have a unique, in-depth-experience that would be hard to duplicate on your own, says Larry Martin, president of Food & Wine Trails, which is hosting 20 wine cruises this year.

But before you book, take a close look. Theme cruises vary widely. They range from small affinity groups that meet on a regular sailing, to thousands of aficionados who take over a cruise ship and create a very different atmosphere from a typical sailing. You'll want to know just what you're booking -- and whether it's right for you -- before you commit.

Partial vs. Full-Ship Charters

The first thing to decide is how big a group you want to cruise with. An entire sailing marketed to those who share the same interest is called a full-ship charter cruise when it's put together by a tour company or travel agency; it's known as a themed sailing when it's hosted by a cruise line. On these trips, everyone onboard is involved in the themed activities.

However, when an affinity group books only some of the cabins on a sailing, it's known as a partial-ship charter, and your group will be surrounded by families, seniors, honeymooners and other vacationers enjoying a typical cruise. Sometimes, special-interest participants are surprised to learn they don't have the ship to themselves.

Full-ship charters are more conducive to in-depth days of activity mingling with fellow enthusiasts. They are also ideal for vacationers who are skeptical of the typical cruise experience or clientele and want to be totally immersed in the onboard vibe created by likeminded people.

A partial-ship sailing can be fun, but know that you'll be surrounded by hundreds who might not share your interests, everywhere from the buffet line to the cocktail lounges. And a special-interest cruise with thousands of passengers hosted by a cruise line might end up being more like a typical sailing, just with extra lectures or special events tossed in.

But partial-ship cruises also can give passengers an insider experience they'd never have on a standard sailing. For example, Sonoma Valley winemaker Diane Wilson of Wilson and Matrix wineries in Healdsburg, CA, is leading about 100 lovers of vino on an Oceania Cruises ship that carries 1,200 passengers. The cruise to Spain, France and Italy features onboard tastings of the family winery's award-winning Zinfandels and Pinot Noirs, plus wine dinners. Shore excursions led by local wine professionals will give cruisers "inside access to the (wine) regions ... cool stuff they can't find on their own," says Food & Wine Trails' Martin. When they're not with the group, oenophiles will have the usual cruising experience on a ship with the other 1,000 or so passengers.

Ultimately, the intimacy of any theme cruise depends on its size and the number of activities in which the headliners participate. An outing with just a few hundred fellow enthusiasts or one that takes over a small ship is more conducive to one-on-one interaction. Yet a full-ship charter offers the reassurance that everyone onboard will have a similar mindset and a sense of camaraderie.

What to Expect on a Theme Cruise

From the moment you board a full-ship theme cruise, expect to dive into the motif. That might come in the form of a pre-sailing concert, Champagne with prestigious lecturers or a welcome kit in your room laying out an exciting and full schedule of events (including chances to party alongside big-name guests). You'll likely have received materials pre-sailing to prepare you for how you'll spend your days and what you need to bring.

Activities will vary greatly depending on the theme itself. For example, during the "World's Largest Super Bowl Party at Sea" cruise, participants join in Bingo-like football pools in the main showroom during the game, a pregame "tailgate party," and cocktail parties with prizes throughout the weeklong sailing. Organizer Kevin Kelly, owner of the Cruises Etc agency, typically hosts about 1,200 football fans on a 3,000-person ship. Fans wear the jerseys of their favorite teams and might decorate their cabin doors with memorabilia, logos or hangings made from team T shirts.

Alaidriale Derway, a spokesman for music cruise specialist Sixthman, says its clients on full-ship "music festivals at sea" really enjoy "the proximity to artists, lack of 'VIP' areas, comfortable accommodations" and vacationing for days alongside their musical heroes. It's usual for band members to chat with fans at cocktail parties, Q&A and photo sessions, and even costume fetes. While events are carefully planned, be prepared for surprises. Sixthman execs say you never know what stairwell concert or jam might break out, especially if cruisers are respectful of the talent, which creates a relaxed atmosphere.

Beyond that painting class with Jane Seymour or political discussion with Michele Bachmann, theme cruises are a good way for enthusiasts to make new friends while participating in activities from morning till the wee hours. The fan-to-fan interaction is just as important as fan-to-band, says Anthony Diaz, chief operating officer of Sixthman. "We have guests that meet up" regularly, he says. And you don't need a singles cruise to find love. Many an onboard match has been made among theme cruise participants who once were strangers, says Kelly.

On the flip side, partial-ship singles cruises don't always guarantee a love-boat experience. These outings often attract people looking for that special someone thinking there will be a sea of mate-minded unwed travelers from which to pick. But know that it's typical for an organizer to book a block of cabins, a meeting room and a group of tables at the same dinner seating. So unless you make a quick connection, you might be sailing solo. You might meet up with fellow singles only at meals or special events, and women usually will be vying for the attentions of a smaller pool of men.

How and When to Reserve

You'll be surprised at the number and range of special-interest sailings available in any year. Some cruise lines list them; another way to find what you desire is to search for your interest and the word "cruise" on the Internet. Headlining artists or experts will often promote the cruises on their web or social media sites, so be sure to follow your favorites. You can always ask a travel agent to help you find the perfect themed sailing.

When it comes to making the booking, sometimes you'll book directly with the cruise line, but, more often, a travel agency or promoter handling a given cruise will handle the booking. Be aware that popular outings can sell out quickly (such as cruises involving a number of popular music acts or a famous celebrity with a big following); sometimes repeat cruisers get first dibs on cabins. Treat the cruise booking like concert tickets, and get on the phone a few minutes before the voyage goes on sale.

Questions to Ask Before You Book

How do you decide if a theme cruise is right for you? After finding a sailing with a theme that's appealing, you'll want to look carefully at the offerings to make sure you know what you're getting.

Assess those in charge of the special events to see what else they've done. You can search the Web for reviews of past cruises and complaints to determine if the promoters live up to their promises. Know what happens if a star attraction drops out and how committed you are once you book.

Review the daily activities and schedule, and make sure what's offered is what you expected. How much will the theme be played out? Will you get to meet a celebrity lecturer or musician, or will the stars do their things and vanish? Is the theme carried out in ways that appeal to you, such as varied kinds of gatherings or events? For instance, a September 2015 sailing on Queen Mary 2 with Crosby Stills and Nash involves three concerts but not an intensive up-close-and-personal roster of activities. This kind of outing might be fun for someone who simply wants to hear good music, but perhaps it's not ideal for someone keen on meeting the stars on a bucket-list trip.

Take a look at the itinerary, and make sure the ports are places you want to visit (though you always can stay onboard if you'd like). See whether the sailing's motif extends to shore excursions, such as tours guided by an archeology, wine, food or photo expert, or concerts in onshore locations. These can be memorable ways to experience a port and get more out of your theme cruise.

Check the size of the ship and the size of the group. Will you be sailing with a desirable number of likeminded passengers? Does the ship seem too small or too big for your taste? If your theme cruise is a partial charter, what kinds of people might make up the rest of the sailing, and will you fit in with the onboard vibe? Each cruise line tends to have a different personality and clientele.

Pricing

You'll likely pay more for a theme cruise than a general sailing, as you'll be getting extra activities and access. A celeb-packed itinerary means bigger bucks are needed to cover the costs of the acts. However, organizers like Cruises Etc's Kelly negotiate their deals far in advance with cruise lines, and "we can build in value-adds and keep the price close" to what the other cruisers will be paying -- or lower than last-minute bookings by the general public -- "because we're bringing such a large group," he says. Look for incentives like free onboard spending money and prizes. Drink vouchers or early-booking pricing also can lower the total cost of a theme cruise.

Organizers also can pair up same-sex singles in cabins, avoiding the dreaded single supplement. (Cruise lines generally charge solo travelers double if they want to stay by themselves in a double-occupancy cabin.) If you're on a cruise with nonstop activities, you might be just as happy with a cheaper, windowless inside cabin as with a pricier outside stateroom, since you'll mainly just be using it to crash. But if you want to socialize with newfound friends, consider springing for larger digs with a verandah.

What to Pack

Choose clothes to suit the roster of activities. On a '60s music cruise? Break out the love beads and bell-bottoms. On a zombie cruise? Those who signed up for one on Royal Caribbean's Allure of the Seas in 2014 needed creative togs to go with makeup provided by onboard pros. A fitness cruise will necessitate yoga pants and stretchy tops, while a political cruise might simply demand everyday vacation-wear (with a campaign T-shirt thrown in for good measure). Scan the schedule to see if a costume bash or super-formal evening is planned. Ask whether any needed equipment will be provided or whether you should bring your own golf clubs, camera equipment, knitting needles, etc.

Vets bring business cards to pass out to fellow cruisers they might like to see again. (Be sure to ink in your cabin number, or have cards with your cabin number printed up in advance.)

Pre-cruise, you might want to get on Cruise Critic's Message Boards to chat with fellow passengers in advance of sailing, or plan a meetup onboard. You also can ask for advice from veteran theme cruisers -- or just build excitement for what promises to be a most memorable vacation.