Berth your boat in Whangarei Harbour's unique marina right in the centre of town.
Hop off the boat and get a great cup of coffee or cool beer at one of the quayside restaurants and cafes. Stroll over to the swimming baths and fitness centre. Take a longer walk through one of the many picturesque native forest walks. The children will love the huge playground. Just a block or so away is also the shopping district, movie theater, medical and dental services, internet cafes ... and very importantly a large low-price supermarket to bunker up with.
All this without the need of a car.
If you do want a car to see more of New Zealand, there are cheap ones for sale or hire in town.
After you have taken care of yourself you can organize some care for the boat. There are four major haul-out facilities in town and a well established boat service industry that survives on their reputation with visiting boats - see links.
Being just a day's sail to world renowned spots like the Bay of Islands, Great Barrier Island, Auckland and the Tutukaka Coast (rated as one of the top dive spots in the world!), Whangarei is a great base to cruise around or just park for a while!