Though New Zealand consists of about 38 islands, it is mainly made up of two large ones, the North Island and the South Island. The two are separated by the Cook Strait and are about 25km apart, though the route the ferries take between the major ports on each island is 94km.
There are two main ways to get between the islands and the method you take will depend on where you want to go and how long you’ve got.
Flying
The main carrier between the islands is Air New Zealand, followed by low budget carriers Jetstar and Pacific Blue. There are multiple airports throughout both the islands but the main ones are Auckland and Wellington on the North Island and Christchurch and Queenstown on the South.
www.webjet.co.nz
http://www.airnewzealand.com.au/
Ferry
The main ferry service between the islands is the InterIslander and runs between the cities of Picton, in the south, and Wellington, in the North.
The ferry ride takes about three hours and can be taken as a basic ferry ride or in the comforts of luxury. The journey itself is a spectacular one and can be considered a tourist attraction as much as a method of transport between destinations. It passes tall green hills and weaves through small islands, and just when all that surrounds you is deep, blue ocean as far as the eye can see, the green peaks of the North Island take shape on the horizon.
The best place to go for ferry services, departures and times is the following website.