A cruise line is a company that operates cruise ships and markets cruises on oceans or rivers to the public. Cruise lines are distinct from passenger lines which are primarily concerned with transportation of their passengers. Cruise lines have a dual character: they are partly in the transportation business, and partly in the leisure entertainment business; a duality that carries down into the ships themselves, which have both a crew headed by the ship's captain, and a hospitality staff headed by the equivalent of a hotel manager.
Among cruise lines, some are direct descendants of the traditional passenger lines, while others were founded from the 1960s on specifically for cruising. The business has been extremely volatile; the ships are massive capital expenditures with very high operating costs, and a slight dip in bookings can easily put a company out of business. Cruise lines frequently sell, renovate, or simply rename their ships just to keep up with travel trends.
A wave of failures and consolidations in the 1990s has led to many companies to be bought by much larger holding companies and to operate as "brands" within larger corporations, much as a large automobile company holding several makes of cars. Brands exist partly because of repeat customer loyalty, and also to offer different levels of quality and service. For instance, Carnival Corporation & plc owns both Carnival Cruise Line, whose former image were vessels that had a reputation as "party ships" for younger travellers, but have become large, modern, yet still profitable, and Holland America Line, whose ships cultivate an image of classic elegance.
A common practice in the cruise industry in listing cruise ship transfers and orders is to list the smaller operating company, not the larger holding corporation, as the recipient cruise line of the sale, transfer, or new order. In other words, Carnival Cruise Line and Holland America Line. for example, are the cruise lines from this common industry practice point of view; whereas Carnival Corporation & plc and Royal Caribbean Cruises Ltd., for example, can be considered holding corporations of cruise lines. This industry practice of using the brand, not the larger holding corporation, as the cruise line is also followed in the member cruise lines in Cruise Lines International Association (CLIA), the list of cruise lines, and the member-based reviews of cruise lines.
Currently the largest (in terms of passenger market share) cruise lines or brands, not holding corporations, include Carnival Cruise Line, Royal Caribbean International, Star Cruises, Norwegian Cruise Line, Crystal Cruises, MSC Cruises, Costa Cruises, Princess Cruises, AIDA Cruises, Celebrity Cruises, and Holland America Line.