Thanks to all who have responded. Here is something from NCL that is the best explanation I have seen so far in regards to cruise passengers:
The government of New Zealand has recently launched an electronic visa called the NZeTA that will be required for all guests not holding New Zealand or Australian passports to obtain prior to their cruise.
The NZeTA visa will be available for purchase via New Zealand's immigration website, or their mobile app, called NZeTA. Guests will also have to pay what is called the International Visitor Conservation And Tourism Levy (IVL) which is done at the same time as the visa application.
NZeTA visa will cost 9 NZD if purchased via the mobile app, and will cost 12 NZD if purchased via the website. The IVL will cost 35 NZD, and price remains the same whether purchased through the mobile app or website. Therefore, total cost will be either 44 NZD or 47 NZD per person to get both the NZeTA and IVL.
WHO NEEDS THE NZeTA VISA?
All guests who do not hold passports from New Zealand or Australia require the NZeTA visa to enter New Zealand by sea (for cruises that start and end in Sydney). Australian permanent residents who do not hold Australian passports also require the NZeTA. All nationalities are eligible to enter New Zealand by sea on a ship with the NZeTA. However, only the visa waiver countries can obtain an NZeTA visa to enter New Zealand by air (for cruises that start in Auckland). Guests from all nationalities that are not part of the visa waiver program (except for New Zealand and Australian passport holders) must get a visitor visa to enter New Zealand by air. This is a separate visa that is also obtained online.
All guests MUST have the NZeTA or visitor visa in order to take any cruise that visits New Zealand ports. It is not an option to detain a guest onboard in New Zealand ports if they do not have the required visa. For cruises that begin in Sydney, we will check for the NZeTA confirmation email from every guest at check in so please print or have the confirmation email available on your phone. Anyone who has not yet applied can do so at the pier, but will not be boarded if they do not receive approval before the ship sails.
Click here to view countries and territories that are visa waiver countries.
HOW LONG IT TAKES TO GET THE VISA:
It is recommended that everyone applies for the NZeTA at least 72 hours prior to travel, as it can take up to 72 hours for the visa to be approved for certain individuals.