You are required, by New Zealand law, to alert the authorities to any snake you see in the country.
There are no endemic species of terrestrial snake in New Zealand, and laws are in place under the umbrella of “bio security” to keep out any and all foreign species, lest they upset the ecosystem. There are no snakes in any zoos or research facilities, they may not accompany travelling performers on tour in the country, and ownership of a snakes as pets is strictly forbidden.
New Zealand does, however, employ snake handlers just in case and these handlers train with live snakes in Australia (where they have all manner of snakes that can kill you). This is an interesting article on the subject.