There are 2 beaches within a reasonable range that are "noted" as being naturist beaches.  Namely Breaker Bay on the wellington peninsula and Peka Peka on the Kapiti coast.  That said NZ has no official nude beaches.  In part because it is thought that creating official nude beaches would potentially attract unsavory types.  That said there is no statute in NZ against being naked in public. The only constraint is that it must not be both deliberate and obscene.  Where one could reasonably expect to see people naked eg. on a beach then no court in the coutry would uphold any action taken.

We have had test cases where people coose to exercise naked, eg. jog or cycle. This was a number of years ago and the courts said it was perfectly reasonable behaviour.  In the case of the cyclist though he was wearing a helmet as required by law.

So accordingly I have swum naked on a number of local beaches and also in the local river swimming holes with out any issue what so ever.  Mostly NZ'ers are a tolerant bunch and they are not going to complain anyhow, however there are always exceptions to this. The single biggest risk here would be posting by some narrow minded individuals on social media, the fear of which is probably one of the biggest inhibitors, but once you have got past that just get on and enjoy life.  

  

Jogging or cycling naked (with the exception of World Naked Bike Ride events) would never be OK in my part of the US.  There has been a WNBR event in Philadelphia right through the main downtown area ("Center City") for the last several years with no repercussions.  COVID this year will be the impediment.

You are both correct. I've seen some of this first hand.