Key Points:

For many New Zealanders, summer is defined by unveiling the barbecue packed away on a corner of the deck, followed by a game of beach rugby or cricket while fresh scallops and crayfish sizzle on the coals.

If you're lucky those delicacies will have been plucked fresh from the sea that morning by an intrepid Kiwi bloke or blokette.

We are, it would seem, a country of scuba divers. But, unlike many other countries, New Zealand hasn't had a great tradition of just look-see divers.

We have a very high rate of diver training and participation, but they mostly become the hunter gatherers.

A good dive is determinedly the number and size of the crays.

But this isn't the case in many other countries. Perhaps because they don't have our abundant kaimoana, but more likely because they have developed dive tourism industries and a well-established no-take dive culture.

However, we do have the dive tourism industry. The Poor Knights, and especially Dive Tutukaka - under the stewardship of astute Aussie Malcolm and his daughter, Kate - have developed a busy dive tourism operation servicing the Poor Knights Islands. This should never have been a hard task.

Just a short boat ride from Northland's coast is one of the very best underwater landscapes that you will encounter anywhere in the world.

The real challenge is to encourage people to come to Tutukaka in the first place, competing as it does with all of the other wonderful locations that New Zealand offers.

The same is true for White Island, although fortunately the mere thought of diving by an active volcano evokes the adventurous child in many of us.

The abstract possibility or risk, no matter how remote, of an eruption while there is an effective stimulus for some.

But, should the overseas tourists be the only ones enjoying our fabulous New Zealand diving spots? We think not.

We have challenged intrepid crayfishers to go diving without a catch bag in the past unsuccessfully, in most cases. But those who do venture underwater to view, rather than gather the wild creatures are treated to a visual symphony.

And not just in a rehearsal hall, in splendid concert hall of the most magnificent proportions.

We are lucky in New Zealand that the natural forces that have shaped our land into interesting contours and formations have also been at work underwater.

Our premium dive locations are first and foremost amazing geological formations that happen to be filled with clear blue water and are home to manyunique species.

For our recent book, Top Dive Sites of New Zealand, we visited and photographed what we think are the top 40 dive locations throughout New Zealand.

There are countless other locations, but this selection is the best (in our opinion) of the accessible ones. And, we believe they are individually unique from one another.

Six of the featured sites are within the Poor Knights Islands marine reserve, which has its own chapter.

What can you write that is fresh about New Zealand's most famed dive location? We don't want tore mind you that Jacques Cousteau named these islands one of the top 10 diving locations in the world.

We don't want to say that, but feel compelled to do so. Why? Because we have yet to meet a single person who has visited the Knights and not emerged from the water with similar enthusiasm.

We could have written a whole book about the Knights (we hope to one day) but in the meantime chapter will do.

When you go diving at the Knights, you will be hovering, or swimming through the rocky remains of an old volcanic field. Th eair-bubble caves, fractured rocks and cathedral-like spaces provide a spectacular backdrop for the thousands of fish that live here.

Abundant fish life has always been associated with the Knights, first noted by American fishing legend Zane Grey in the 1920s.The rest of the book includes dives from Wellington's South Coast, the Hauraki Gulf, White Island, Stewart Island and another chapter on Fiordland, a location that couldn't be any further from the Poor Knights, yet is on a par with it.

Blue Maomao Arch, Poor Knights
Afternoon light pours into this large underwater tunnel that is teeming with fish ... Nearby Labrid Channel provides a perfect ending for a dive.

Northern Arch, Poor Knights
This is a challenging but exhilarating dive. The deep underwater archways not very wide, and current flows through most of the time, attracting schools of fish and, if you're lucky, schools of short-tailed stingrays in summer.

Tatapihi (Groper Island), Mokohinau Islands
This island pops up out of very deep water and is a fish magnet. The fish are dense, the inky water deep, and invertebrate life prolific.

Twin peaks, Great Barrier Island
These pinnacles that arise from the sea floor and the regular currents foster an extraordinary biomass fish of all types. Invertebrates of all colours, sponges of all shapes are prolific here.

Honeycombe, Hongiora Island, Alderman Islands
This vast cave system makes uninteresting and safe dive. A handheld torch reveals dense colourful invertebrates that cover the cave walls and the large boulders on the sea floor.

Spanish Arch, White Island
This is an underwater arch on the submerged edge of White Island that sits in a vast and varied underwater seascape. Hammerhead sharks are often seen here too.

Hole in the Wall, Kapiti Island
This can be a turbulent swim through caused by the ever-present current. With current comes prolific fish life and a cave smothered with brightly coloured jewel anemone.

Bunker Islets Seal Dive,Stewart Island
This is like entering a seal daycare centre, and the experience is simply extraordinary. This fur seal breeding colony is probably best snorkelled.

As soon as you enter the water, you'll be mobbed by playful, curious and confident seal pups darting all-around you.

Te Awaatu Channel, Doubtful Sound
In Doubtful Sound's only marine reserve, it is possible to experience nearly all of the diverse habitats that Fiordland has to offer. In a single dive, you can see black coral trees, zooanthids, seapens and redhydrocorals.

Penguin Cove, Milford Sound
This Milford Sound marine reserve is geologically diverse a deep drop-off, sandy bay, undulating sandy slope creating unique habitats that are not often seen together in one location.

Gillian Torckler and her husband, Darryl Torckler, wrote Top Dive Sites of New Zealand. Published by RaupoPenguin, $40. Available now.