These slivers of land, either owned or leased by major cruise lines, offer certain staples across the board, from BBQ buffet lunches to water-based shore excursions. But beyond their cookie-cutter similarities, they have evolved over the years to include playgrounds, water parks, bars, shopping areas, nature trails and even tram systems that shuttle visitors to and fro.
What can you expect from a private island day? Here's what you need to know.
You don't need to spend money. Beach access, lounge chair and hammock use, a buffet lunch and basic beverages (water, iced tea) are included in your cruise fare. Volleyball and Ping-Pong are often free, as are kid play areas.
But if you do, you can use your cruise card. Buying booze, souvenirs and other extra-fee items? In most cases, there's no need to bring cash. Private islands are an outpost of your cruise ship and charge nearly everything to your cruise card. Exceptions are purchases made in the markets in Half Moon Cay and Labadee, from Princess Cay's local vendors and at the post office on Castaway Cay.
Beach toys cost extra. If you want pool noodles, inflatable rafts, snorkel gear or even clamshell shades for your lounge chair, you'll need to pull out the aforementioned cruise card. Consider bringing your own beach toys and snorkel gear to save money.
Private islands offer shore excursions. They vary by island but might include snorkeling trips, zip-line rides, horseback rides, kayak trips and parasailing. Buying access to over-the-top water play areas and waterslides also counts a "tour." All cost extra.
You can rent a private cabana. If you want an exclusive retreat with comfy lounge furniture and extra perks, you can reserve a private cabana. Fees and locations vary -- some sit above the water while others are right on the beach -- but the rentals typically include the services of a cabana steward, free floats or snorkel gear and a shaded indoor/outdoor space to relax, stow your stuff and use as a home base throughout your day. Book as far in advance as possible, as cabanas sell out; some are reserved for VIP passengers (those in suites and high-level loyalty program members) but offer a waitlist for average Joes if they don't book out completely. Check the Private Islands boards to find out which cabanas are ideally situated and best for your family's needs.
Many islands have more than one beach. If the first beach you see looks crowded, keep walking. There are a variety of spots for sunbathing; some lines even designate family, teen, kid and adult beaches and play areas.
You might not be the only ship in port. You might have to share your exclusive beach with cruisers on a sister ship. It will certainly be more crowded with double the number of passengers in port, but Cruise Critic members report there's usually plenty of sand space, though lines at lunch do get excessive.
You can come and go. Just like in other ports, you can come and go to and from the ship as you please, so you could head back for lunch or spend the morning onboard and the afternoon on the beach. Just note that many private islands require tender service, though the ride should be quick.
Whether you're itching to know which line offers the biggest and best or you're just wondering what to expect on your next private port call, read on to check out our six private island port reports.
The Line: Disney Cruise Line
The Lowdown: Castaway Cay is an ultra-tidy, 1,000-acre splash of sun and sand located in the northern Bahamas. Owned by the Walt Disney Company, the island is used exclusively for Disney passengers -- though alert cinephiles might also remember it as the spot where Tom Hanks finds his mermaid (Daryl Hannah) in "Splash." Read the full Castaway Cay cruise guide.
The Line: Royal Caribbean
The Lowdown: CocoCay, formerly Little Stirrup Cay, is a Bahamian island located between the popular cruise ports of Freeport and Nassau. In 1990, Royal Caribbean started leasing the 140-acre plot of land, which features beaches, shopping venues and activities exclusively for passengers sailing with RCI or sister line Celebrity Cruises. Read the full CocoCay cruise guide.
Great Stirrup Cay
The Line: Norwegian Cruise Line
The Lowdown: Norwegian Cruise Line's Great Stirrup Cay -- located in the Bahamas' Berry Island chain, 130 nautical miles due east of Fort Lauderdale -- is a 250-acre island. The cay features dining and bar areas, private beachfront cabanas, a straw market, a kid-friendly Aqua Park and more. Read the full Great Stirrup Cay cruise guide.
The Line: Princess Cruises
The Lowdown: Exclusive to Princess Cruises passengers on Eastern and Western Caribbean itineraries since 1992, Princess Cays -- located 70 miles east of Nassau, on the southern tip of the island of Eleuthera -- comprises 40 acres that offer more than 1.5 miles of white-sand beaches, food, water sports and even shopping. Read the full guide to the Princess Cays cruise port.
Half Moon Cay
The Line: Holland America
The Lowdown: In 1997, Holland America Line purchased Little San Salvador from its previous owners for $6 million. Today, the 2,400-acre island is known as Half Moon Cay and serves as a private retreat for passengers on the line's Caribbean and Panama Canal sailings. Carnival ships also make use of the port. Read the full guide to the Half Moon Cay cruise port.
The Line: Royal Caribbean
The Lowdown: Royal Caribbean's Labadee is a 260-acre private beach resort carved out of Haiti's rolling, densely forested north coast. A typical day in port might include snorkeling, filling up a plate or two at the all-you-can eat BBQ, zipping across the water on the 2,600-foot-long Dragon's Breath Flight Line or snoozing soundly in a beach chair. Read the full guide to the Labadee cruise port.