It was a 21km walking loop with 750 metres of uphill. We did the lookout extension between orongo bay and russell - but i dont recommend it as a must do.
the section from paihia to opua goes along rocks and boardwalks. it needs to be low or a few hours either side of low tide. it winds in and out of bays. its not well marked after the bridge and then follow the trail and turn right about ten metres after the white fence.
the boardwalks along the trail are great and its very diverse from coastal, to lovely forest, raupo, mangroves. the last 8km was a disappointing as it seemed to lose the trail and we were walking beside a road, or a scramble up a fenceline.
Enjoyed lunch in Russell and then ferry back to Paihia. i recommend the walk for any moderate fitness and its a great way to see the area