There are several cruise lines that own private islands, parts of islands, or resorts exclusive to their cruise passengers, and a day at these private retreats is included in many of their Bahamas and Caribbean itineraries.
These ports of call are small getaways that basically offer a day at the beach swimming, sunbathing, relaxing, with some water sports available. They usually have a bar, a place to get something to eat and a souvenir shop. Some have volleyball courts on the beach, yoga classes, massages, and water slides.
Shore excursion options include snorkeling or fishing trips, horseback riding, biking and hiking, glass bottom boat tours, stingray adventures, and more. The choices vary by island. These private retreats are one of the ways cruise lines make their money since every dollar you spend here, at least some of it, goes into their pocket.
These islands have become quite popular with cruise passengers so there are many itineraries that include a day here. Some itineraries actually stop here more than once. Most are located in the Bahamas and, due to their size, have no large dock so passengers are tendered in.
In the Bahamas, Princess Cruise Line has Princess Cays; Norwegian has Great Stirrup Cay; Disney Cruise Line has Castaway Cay, and Holland America and Carnival share Half Moon Cay (Little San Salvador).
Royal Caribbean and Celebrity have CocoCay (Little Stirrup Cay) in the Bahamas and Labadee, a private resort on the northern coast of Haiti.
Costa Cruises has a private beach on Catalina Island, offshore from La Romana on the southern coast of the Dominican Republic.