Now at rest but still in service

Diving on the HMNZS Canterbury is an ethereal experience.

Conor MacHugh honours the Canterbury in a watery home.

Julia gives the all clear and we drop over the side, following the white mooring line down to the comms tower on top of the bridge. At first, we see nothing. Then vague lines become real as the bridge takes shape. And the ship looms out of the blue, spectral in fine russet and olive algae.

We pulled off the Russell road on Friday night and were greeted by Northland Dive owners Julia and Shane. Soon we were sitting at the long table with a tea and beer, meeting divers and guides. The kitchen is familial, the company convivial and excited, for this weekend we will dive New Zealand's newest major wreck, HMNZS Canterbury, scuttled 20km from here at Deep Water Cove in 2007.

Photos and bovine accessories alert me to the fact our dining room was once a cow shed, and we prise the story out of our hosts. The couple bought a block with an old milking shed 10 years ago as a place to store their boat and pursue their passion for diving. On their first dive, Shane promised he would one day sink a boat here. Friends and their friends began to arrive to dive and share the cow shed. With many improvements and much investment the couple had a business.

Meanwhile, the Scots-built Canterbury was nearing the end of her active career. Launched in 1970, she sailed to the Persian Gulf, Mururoa atoll and East Timor. As the ageing ship was decommissioned in 2005, a tender process was begun. With other dive businesses and enthusiasts the documentation was completed rapidly. They approached Ngati Kuta and Patukeha about sinking the ship in the waters of Maunganui Bay.

The iwi suggested a joint venture and a trust was formed. Outlandish schemes for floating hotels and restaurants were quickly dismissed and the ship was sold as a dive site to the trust for a symbolic dollar. She was scuttled by explosives in November 2007 and lies at 36m in the middle of the cove throughout which the iwi maintain a marine reserve.

Once above the wreck, we get an impression of her size and bulk, 113m long and nearly 3000 tonnes of steel.

A wreck is a different experience to diving a wall or a reef. It is man-made, frozen, yet the ghost of its function.

We pass through a door and into a helicopter hangar the size of a double garage. Up close the ship loses its ethereal quality and you examine the familiar in a new light. And then we are like kids in a scrap heap, coasting along the gunnels and the broad deck, poking into the holes where the guns stood and playing at captain in the bridge. A phone on the foredeck has slapstick and bubbles pealing out of us.

Thanks to the iwi's rahui, marine life is abundant. Kingfish flicker past and giant snapper lazily survey our progress.

There is a huge scorpion fish on the deck so adept at camouflage I only learn about him after we surface. Electric blue jewel anemones cling to the railings and schools of fish wheel and turn.

All too soon it's time to head up, all grinning broadly after everyone's best dive in living memory.

As we settle into a post-dive beer there is no question. We will return.

After 25 years and almost a million nautical miles the Canterbury is at rest, but still in service.