If you are lucky enough to arrive in a yacht or small vessel, then there are strict customs protocols for notification & process that must be followed, but it's likeliest under these circumstances that your skipper will know the ropes! For most other people, arriving by sea means arriving on a cruise ship.
Cruising New Zealand is a fabulous way to see the diversity of landscape & wildlife that NZ has to offer. New Zealand is now a regular destination on round-the-world cruises, rivalling anywhere else on the globe. The most popular places for starting a cruise to New Zealand are Australia (Sydney, Melbourne & Brisbane) and the South Pacific (Vanuatu, New Caledonia, Fiji, Tahiti), as well as New Zealand itself. With a thriving cruise schedule, you can board a cruise in NZ & return back to the same port having crossed the Tasman Sea or the South Pacific or simply explored the wonderful richness of New Zealand's shores.
From the Bay of Islands in the tropical North to Stewart Island off the southern tip of the South Island, the sheer range of environments is staggering. Fiordland affords scenic cruising through a World Heritage Site, Nelson encompasses three National Parks, while Kaikoura gives you unsurpassed access to whales and dolphins; not to mention the off-ship excursions around the country.
The arrival protocols are very similar to arriving by plane, which means that the focus will be primarily on biosecurity. The passenger arrival card everyone has to fill out before passing through customs requires you to declare any food, animal or plant products (including wood), anything biological & any equipment or items that have been used in any outdoor activities. You also need to declare if you've been to any wilderness areas or had any contact with non-domestic animals in the past 30 days. The prime purpose of all this is to ensure that no-one unwittingly imports any non-native biology that could severely disrupt the ecology of New Zealand. Given the country's natural isolation its wildlife has a much less developed defence against foreign species. If you suddenly remember something at the last minute, there are 'amnesty bins' at all ports, where you can anonymously throw away suspect goods before you go through declarations.
The easiest way to ensure you have no problems with biosecurity is to leave any problem items at home (check the latest, full list here), or at the very least, on board your ship. Of course, there are also the normal identification - passport & visa - requirements, and questions about your travel, accommodation, finance & acquaintances. Each NZ port has its own rules and procedures for disembarkation and pickup.
Bay of Islands (Waitangi, Paihia and Russell). At Waitangi, passengers need to use a tender to reach shore. The wharf is on the Treaty Grounds & it's just a 10 minute walk to the Treaty House. From there, free shuttles can take you to Paihia i-SITE visitor centre, less than 5 minutes away, from where you can also catch a ferry to explore Russell.
Auckland is the main hub for cruise ships & most democratic port in NZ. Located in Auckland's CBD, close to hotels, transport hubs, shopping, dining and other attractions, anyone can enter the port & passengers can leave it on foot.
Tauranga, in the Bay of Plenty is the port that gives you access to Rotorua and Hobbiton, as well as nearby Mount Maunganui. Passengers can disembark directly at the berth & you can walk out or shuttles can take you to the i-SITE centre in town.
Napier's berth is about 1Km north of the town in a working port (to enter the port you need a special ticket) with no pedestrian access, so free shuttle buses carry passengers into town. Once there, most attractions are within easy walking distance.
Wellington has several cruise ship berths, with most arriving at Aotea Quay, a good 20 minute walk from the central city, or a 5 minute free shuttle ride. Because of the distance and as you need a special ticket to enter the port, anyone meeting a passenger would be best advised to wait at a central point in the cruise terminal.
Akaroa, the gateway to Christchurch, is a quaint French inspired township in the centre of an ancient volcano. Tenders will convey you to the wharf on the south side of the village, close to shops and cafes. You can take the transport to Christchurch, about an hour and a half away, from where you could start your ride on the TranzAlpine train, or enjoy the local activities: boat cruises, dolphin safaris or wine tastings.
Dunedin's cruise ship berths are in the working port of Otago, so a special ticket is required to enter, but passengers may disembark & leave the port on foot. There are two berthing facilities, Port Chalmers about 13Km from the city & Port Dunedin which is closer. Shuttle services will drop you off by the Octagon, the very centre and a local landmark near the i-SITE visitor centre.