A passport IS required on the cruise you are taking to Hawaii. The island of Fanning requires passports since they stop at that location, regardless of whether you get off or not.
That's changed. Itineraries that call at Fanning Island require a passport because Fanning Island is part of the Republic of Kiribati, but few ships now call there.
>> The "NCL America" ships (Pride of Aloha, Pride of America, and Pride of Hawaii) are of U. S. registry, so they are exampt from the restrictions of the Jones Act on vessels of foreign flag. Thus, they can operate cruises that call only at ports of the United States. As a result, they do NOT call at Fanning Island on their cruises to the Hawai'ian Islands. In fact, these cruises probably do not require any proof of citizenship because they are entirely within the United States.
>> Celebrity's and Princess's round trip cruises to Hawaii from either Los Angeles have a service call at Ensenada to meet the requirement to call at a foreign port. Thus, these cruises do not require passports through the end of this year.
Note that a change in U. S. law requires passports for all persons coming into the United States by air or by sea after 31 December 2006. This requirement will apply to all cruises to the Caribbean, Canada/New England, the Panama Canal, the Mexican Riviera, and Alaska as well as to the Hawaii cruises that operate from the U. S. west coast.