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.
Because of mergers and consolidations, a cruise line may also be a brand of a larger holding corporation.
Cruise lines operating ocean and river ships can be found in both lists.
As of 2021[update], the cruise industry was estimated to be around US$23.8 billion with 13.9 million passengers per year.
The list also includes the combined market share of each of the cruise line holding companies: Carnival Corporation & plc, Royal Caribbean Group, Norwegian Cruise Line Holdings, TUI Group, and Genting Hong Kong.