On a walk along North Piha came across this spider actually in the wave zone on the shore. Auckland Council staff reckon its a Banded Tunnelweb Spider Hexathele hochstetteri, which is noted to be very fast which we observed as it raced around. This spider builds a tunnel shaped nest among leaves with “trip lines” coming out from the entrance that catch insects as you can see at the following web sites. Feel rather guilty about leaving it down there among the waves now I know it lives in the forest. Hope it found its way home.
http://www.terrain.net.nz/friends-of-te-henui-group/spiders/branded-tunnelweb-spider.html