Luxury — but not all inclusive — cruise line Azamara doesn't outright prohibit younger passengers, but there is a lack of kid-focused activities available on board. The general atmosphere of Azamara's smaller ships is geared more towards adults, offering various conveniences that passengers above the age of 18 are sure to enjoy.

15. Azamara Luxury Cruises

Regent Seven Seas advertises itself as the only true all-inclusive cruising option, including unlimited alcoholic beverages, shore excursions, specialty dining, airfare, airport transfers, and Wi-Fi access. While not strictly an adults-only cruise line, it doesn’t offer any kind of service that looks after or entertains children.

14. Regent Seven Seas Cruises

Windstar Cruises has a policy favoring adults, with age restrictions that prohibit young children and prevent groups of college students unaccompanied by adults. Entertainment options are tailored more towards adults' interests than children's, and there are third person charges for any third party who ends up in a standard cabin (minors included).

13. Windstar Cruises

Lindblad places a heavy emphasis on research and exploration, with unique destinations through the Arctic Ocean, Galápagos Islands, Subantarctic Islands, and Easter Island. Unlike relaxation-based cruises on this list, Lindblad caters most directly to travelers seeking a one of a kind adventure in some of the most remote regions of the globe.

12. Lindblad Expeditions

Aurora Expeditions is aimed at thrill seekers, prospective adventurers, photographers, and those who want to see and experience once-in-a-lifetime sites. Capitalizing on its unique array of destinations, Aurora takes travelers to venture to some of the most far-away areas on Earth — and requires a signed medical form three to six months before cruising.

11. Aurora Expeditions