Running a cruise line is a funny thing. On the one hand, your job is to take your passengers to new and exciting places and entertain them with things they've never experienced before. On the other, those same passengers will turn on your in a minute if it rains, if the destination isn't what they expected, or if they stub their big toe on a shore excursion.

What's the solution? Control. And when you couple control with increased profits, you have two of the possible reasons behind (a) larger, resort-like vessels such as Royal Caribbean's Voyager, Freedom, and Oasis classes, and (b) the fact that so many cruise lines operate their own private resorts in the Caribbean and the Bahamas.

Private resorts are the perfect business solution to the fact that most cruise destinations have actual people living in them -- not to mention thousands of other cruise passengers who may be swarming the place when you arrive. Recent experiences I've had in St. Thomas, Cozumel, and Nassau were more about traffic jams and crowded shopping malls than frozen margaritas, breezy beaches, and crystal-blue water. At the busiest ports, where 10,000 cruise passengers may have poured off the megaships the same day as you, it's good-bye relaxing beach paradise and hello queues, crowds, gridlock, and pushy touts.

The cruise lines' private resorts, on the other hand, are designed for one or two ships tops, and have two simple missions: (1) provide passengers with a sane, hassle-free place to enjoy a day at the beach; and (2) keep more of the bar, souvenir, and excursion profits in the cruise line's pocket. On the plus side, they're definitely less hectic and commercialized than the busiest regular ports. On the downside, they offer few hints of true Caribbean culture. Whether you enjoy them or not depends on what you're expecting out of your day.

Here's a list of all private islands, peninsulas, or beaches operated by the cruise lines and offered as a port of call on many of their Caribbean and Bahamas itineraries. Note that aside from Disney's Castaway Cay, none of the islands has a large dock, so passengers are ferried ashore by tender.

Celebrity Cruises & Royal Caribbean

Many ships of sister lines Royal Caribbean and Celebrity stop for a day at one of the line's two private beach resorts, CocoCay and Labadee. At both, organized children's activities include beach parties, volleyball, seashell collecting, and sand-castle building.

At CocoCay (aka Little Stirrup Cay), an otherwise uninhabited 140-acre landfall in the Bahamas' Berry Islands, you'll find lots of beach, hammocks, food, drink, and watersports, plus such activities as limbo contests, water-balloon tosses, relay races, and volleyball tournaments. Kids big and small will like the aqua park that includes a floating trampoline, water slides, and a sunken airplane and schooner for snorkelers. The newest gimmick: Kids 3 to 8 can now hop in battery-operated mini race cars for what the line bills as a "special driving adventure" on the Fisher-Price Power Wheels Track. For something quieter, head for Wanderer's Beach; it's a longer walk from the tender pier than the other beaches, so it tends to be less crowded and quieter. Its calm surf and ultra-soft sand make it perfect for families with young children.

Labadee, an isolated, sun-flooded, 270-acre peninsula along Haiti's north coast, is so completely tourist-oriented that you'd never know it was attached to the rest of poverty-stricken Haiti. That said, though, Labadee is a rarity among the cruise lines' private islands in that it does give you a real glimpse of island culture. At the straightforwardly named "Folkloric Show," a large, colorfully costumed troupe performs Haiti's distinctly African brand of dancing, drumming, and song, while acoustic bands at the various bars and restaurants play a kind of music that was a precursor to reggae and other Caribbean styles. Five beaches spread around the peninsula are progressively less crowded the farther you walk from the dock, where enormous tenders make the short ride to and from the ship. For children, there's the pirate-themed "Splash Bash" area with water sprinklers, fountains, and spilling buckets. There are also floating trampolines, inflatable iceberg-shaped slides, and water seesaws. Kayaking and parasailing are offered from a dock nearby. The latest rage is a new 2,800-foot-long zipline called Dragons Breath, which takes you over the water of Dragons Tail Beach. At the center of the peninsula, the Haitian Market and Artisans' Market are the port's low points, full of cheesy Africanesque statues and carvings, with touts trying to lure you in.

Costa Cruises

Passengers on Costa's eastern Caribbean itineraries spend one day at Catalina Island, off the coast of the Dominican Republic. This relaxing patch offers a long beach fringed by palm trees, with activities such as volleyball, beach Olympics, and snorkeling. The area adjacent to the tender dock is the busiest spot (as is true on all the islands), but if you walk down the beach a bit you'll get a quieter, more private experience, even if the coastline does get a little rocky as you get farther out from the dock. Costa provides cruisers with floating beach mats free of charge (most lines charge for them), while a local island vendor rents jet skis and offers banana-boat rides. The ship's spa staff also sets up a cabana to do massages on the beach, and locals often roam around offering them, too. Vendors also sell coconuts for a couple of bucks apiece, hacking the end off and adding a straw so you can get at the milk. After you're finished, take it back and they'll whack the thing to pieces with a machete and scrape out the tender coconut meat. Music and barbecues round out the day, and there's also a strip of shops hawking jewelry, beachwear, and other souvenirs.

Disney Cruise Line

A port of call on all Disney Magic and Disney Wonder Caribbean/Bahamas cruises, 1,000-acre, 3x2-mile Castaway Cay is rimmed with idyllically clear Bahamian water and fine sandy beaches. Disney has developed less than 10% of the island, but in that 10% guests can swim and snorkel, rent bikes and boats, get their hair braided, shop, send postcards, have a massage, or just lounge in a hammock or on the beach. Barbecued burgers, ribs, fish, and chicken are available at Cookie's Bar-B-Q, and several bars are scattered around near the beaches. Kids enjoy the barnacle-encrusted 175-foot Flying Dutchman ghost ship from Pirates of the Caribbean anchored just offshore, while adventurous adults can sign up to go parasailing.

The island's best quality is its accessibility. Unlike the other private islands, which require ships to anchor offshore and shuttle passengers back and forth on tenders, Castaway Cay's dock allows guests of Magic and Wonder to just step right off the ship and walk or take a tram to the island's attractions. Families can head to their own beach, lined with lounge chairs and pastel-colored umbrellas, where they can swim, explore a 12-acre snorkeling course, climb around on the offshore water-play structures, or rent a kayak, paddle boat, banana boat, sailboat, or other beach equipment.

Teens have a beach of their own, where they can play volleyball, soccer, or tetherball; go on a "Wild Side" bike, snorkel, and kayak adventure; or design, build, and race their own boats. Parents who want some quiet time can drop preteens at Scuttle's Cove, a supervised children's activity center for ages 3 to 12 where activities include arts and crafts, music and theater, and scavenger hunts. An excavation site here allows kids to go on their own archaeological dig and make plaster molds of what they find -- including a 35-foot reproduction of a whale skeleton.

Meanwhile, Mom and Dad can walk, bike, or hop the shuttle to quiet, secluded Serenity Bay, a mile-long stretch of beach in the northwest part of the island, at the end of an old airstrip decorated with vintage prop planes for a 1940s feel. Full massages are available here in private cabanas open to a sea view on one side (sign up for your appointment at the onboard spa on the first day of your cruise to ensure that you get a spot), and the Castaway Air Bar serves up drinks.

All-terrain strollers with canopies and beach wheelchairs are available free of charge and adult- and child-size bicycles are available for rent, while a recently lengthened bike/walking path lets you stretch those hamstrings. Just don't go looking for scenery or wildlife -- at best, all you'll see will be the occasional bird or leaping lizard.

Holland America Line

Located on the Bahamian island of San Salvador, 2,500-acre Half Moon Cay is a port of call on most of Holland America Line's Caribbean and Panama Canal cruises. Families will appreciate the water park at one end of the beach (closest to the tender pier), where there are three water slides on the sand for young children, as well as a couple for teens. Just offshore in the shallow turquoise sea, a cluster of floating toy animals is tethered to the seafloor and perfect for climbing. Other highlights of the beach area include massage huts as well as air-conditioned, beachfront cabanas available for rent. A couple hundred bucks will buy you butler service and an open bar.

Away from the main beach area and accessible via a short tram ride, shore-excursion opportunities include horseback riding and a visit to a 150x75-foot water pen where you can pet and feed tame stingrays. You can also sign up for windsurfing, snorkeling, kayaking, scuba diving, deep-sea fishing, parasailing, sailboarding, or aqua-cycling. Lunch facilities, several bars, a playground, and even nature trails through a wild bird preserve round out the island's offerings.

MSC Cruises

Most of MSC's Caribbean cruises spend a day in Cayo Levantado, a beach-rimmed, palm-tree-lined rainforest island off the northeast coast of the Dominican Republic's Samana Peninsula. As at all the other private islands, passengers may choose to flop on the beautiful white-sand beach, take a tour (including jeep safaris and a whale-watching cruise), or go snorkeling or swimming. There are beach chairs, umbrellas, and walking paths, plus tables for an open-air lunch. What you won't find, though, are a playground, hammocks, or massage facilities. One other difference: A day at this beach is considered a shore excursion, so passengers are charged a flat rate if they want to play here.

Unlike the other private islands in this section, Cayo Levantado actually isn't private at all: It's run by a Dominican company with whom MSC has scheduled port calls. The line also makes calls at the Dominican Republic's port of La Romana, where passengers can enjoy the 7,000-acre resort Casa de Campo.

Norwegian Cruise Line

NCL's private island, Great Stirrup Cay, is a stretch of palm-studded beachfront in the southern Bahamas, and was the very first private resort developed by a cruise line in the Caribbean. It's also the most cramped of the bunch, and part of the shoreline is very rocky. Still, after a piƱa colada or two, you probably won't notice its flaws. Bar, lunch, and watersports facilities are hopping, hammocks are strung between palms, and music is either broadcast or performed live. Passengers can ride paddle boats, sail Sunfish, go snorkeling or parasailing, hop on a banana boat, join a game of volleyball on the three deep-sand courts, get a massage at one of the beachside stations (though they're not very private or quiet), or do nothing more than sunbathe all day long. For kids, organized activities include volleyball tournaments and sand-castle building, but there's no actual playground here.

Princess Cruises

Most of Princess's eastern and western Caribbean itineraries offer a stop at Princess Cays, a 40-acre beachfront strip off the southwestern coast of Eleuthera in the Bahamas, pretty much cut off from the rest of the island. The half-mile of shoreline allows passengers to swim, snorkel, and make use of Princess's fleet of Hobie Cats, Sunfish, banana boats, kayaks, and pedal boats. (If you want to rent watersports equipment, be sure to book while aboard ship or even online, before your cruise, to ensure that you get what you want.) There's also a beach barbecue, but no live music or massage facilities. Anyone who wants to get away from it all can head for the several dozen tree-shaded hammocks at the far end of the beach. For kids, there's a supervised play area with a sandbox and a pirate-ship-themed playground. The Princess shop sells T-shirts and other clothing, plus souvenirs of the mug-and-key-chain variety, and local vendors set up stands around the island to hawk conch shells, shell anklets, straw bags, and other crafts, and to offer hair braiding.

Regent Seven Seas Cruises

Though not affiliated with Princess, the luxe ships of Regent Seven Seas do make stops at Princess Cays (see above) on some of their Caribbean itineraries.

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