At 7.8 metres, Cave Cruzer is the only vessel of its size operating in Mercury Bay, small enough to navigate inside caves and blowholes that larger boats with cabins or roofs cannot enter, open-topped so nothing blocks your view of the volcanic ceilings above. Between stops, Brian opens the throttle.

This is a two-hour tour along 24 kilometres of protected Coromandel coastline and Islands. You will cover ground most visitors never reach, at speed. Shakespeare Cliff, named by Captain Cook in 1769, passes as the volcanic coastline opens up heading south. Ancient blowholes and cave systems carved over centuries line the route, and Cave Cruzer can go inside them, tide and swell permitting.

Cathedral Cove is the centrepiece of the tour. Te Hoho Rock, the Sleeping Dragon formation, and the filming locations from The Chronicles of Narnia: Prince Caspian are all here, seen from the water in a way most visitors never experience. Further along, Whale Cave on Mahurangi Island and the hole in the rock at Poikeke Island are named landmarks that can only be seen by boat.

The tour heads inside Orua, New Zealand's second-largest sea cave where Brian cuts the engine and plays music so you can hear what 700 cubic metres of rock does to sound.

As a bonus, weather and tide conditions permitting, it is possible to snorkel in Gemstone Bay or jump off the rocks at Whale Cave. If cave, blowhole access or snorkelling cannot go ahead due to weather or tide conditions, travellers will receive a full refund.

Brian, your guide, has been running these waters for years. His humour, music and local knowledge of the geology, Maori history, and marine life of Mercury Bay - Te Whanganui-a-Hei - is what separates this from a boat ride.

Travellers can cancel up to 24 hours in advance to receive a full refund. If the operator cancels, travellers will receive a full refund.