This track is one of our favorite exercise outings when in the Waikere River anchorage off of Opua. The track is just under 6km and 2.5 hours one way.
You can park your dinghy at the Opua Cruising Club, or on the dinghy pontoon next to the Opua Store. And as a reward for doing the whole track to Paihia and back, you can have a seriously good espresso coffee at the Marina Cafe.
The Opua-Paihia walking track is volunteer-maintained. Here are all the Department of Conservation tracks around the Bay of Islands (there are a LOT of wonderful tracks).
Adagio Journal 