In reply to Liam Dangerfield:
As you wanted to be patronised...
Travel insurance can cover a wide range of things including (but not limited to) personal accident, personal liability, repatriation, cancellation, delays, personal possessions (including replacement passport) and sometimes accidental death etc blah blah.
As others have said, NZ care for visitors very well, the flip side is it's impossible to sue people if they don't. For example, if the jet boat driver only has his RYA level 2 rib handler and flips it across a narrow river permanently maiming you forever.
YOU need to decide whether you want to take the risk on these things and whether you want cover for them. Consider that repatriation if you were seriously injured is very, very expensive and NZ is a very, very long way away. I wouldn't want to spend 18 months recuperating from a massive spinal injury 48 hours away from my nearest and dearest for example. That is the very real benefit to travel insurance IMO. I have a rule, only insure what you can't afford to replace, or pay for. Money, bags, passport - all easy to replace, especially in a friendly country who speak English. Getting home without the use of your legs? Difficult. We're talking hundreds of thousands of pounds, at least. I've seen claims of nearly 2 million. (Obviously, chances are TINY)
When buying it, make sure you read the small print. Look for a policy that covers the WHOLE duration of your trip and covers you for work. People often look to make sure bungee jumping is covered, but many insurers won't cover you if you're going out to work there.
STA are quite good for this sort of thing (no personal connection, I worked for a cheapo, budget provider) but there are others. I would personally consider repatriation insurance at the very least.
HTH?