Along the Hokianga Harbor, there is a stretch of beach that contains some interesting rock formations called the Koutu boulders. My mother-in-law and I walked along the beach and it took us the best part of two hours.
Most sites say it's an 'easy' walk if you go two hours either side of low tide. Maybe if you're 25 and have done a decathlon or two. But for two, ahem, older gentleladies who were looking for a stroll down the beach, not so much.
But we were determined to clamber over rocks and get to the other end--mostly, because we didn't think we could get back up the steep bank that we came down from the car.
And, by golly, we can say we walked from one end to the other!
I didn't see any 20 foot-tall concretions like they said we would (whoever 'they' are), but some were pretty big. I am 6 feet tall (that's me in the blue) and several were taller than me. I hope you enjoy the views.