For more than a century, treasure hunters have made their way to the Three Kings Islands. Some came in search of real treasure; the gold and silver coins that sank with the steamer SS Elingamite in 1902. Others, such as big-game fishers and divers, were looking for biological wealth—kingfish, hapuku and marlin that idle through the clear water, and groves of swaying seaweeds common around the island group.

The first people to visit—and the only ones to ever live permanently on these islands—were Maori who named them Manawatawhi. The first Europeans to see them were Dutch explorer Abel Tasman and his crew on January 6, 1643. They bestowed the name Drie Koningen Eyland (Three Kings Island), after the biblical magi who brought gifts of gold, frankincense and myrhh. Tasman and his men were in search of their own treasure too—precious fresh water—but rough seas battering the islands’ steep cliffs denied them an opportunity to land, and they were forced to sail on.

It’s a familiar tale. High seas and bad weather have been the curse of many who have tried to reach the Three Kings, for all must cross a gauntlet of fierce tides that encircle New Zealand, accelerating as they rush back and forth across the top of the North Island. The Three Kings Islands lie 53 kilometres north-west of Cape Maria van Diemen, yet even that far away they experience these great daily movements of water. The tidal effects are magnified around the remote islands as flows collide with the submarine topography of the Three Kings Bank before hitting the steep walls of the islands themselves.

Below the tumultuous surface flows there is more water action, as vast internal tides become entrained within layers of water at depth. Like a submarine ocean swell, massive internal waves slowly build and then break, propagating across hun­dreds of kilometres of ocean—their effects are felt nearly as far away as Norfolk Island.

Adding to the dynamic interplay of water flow and topography, upwellings bring deep, cold water to the surface as great ocean cur­rents such as the Tasman Front coming across from Australia and currents flowing around northern New Zealand hit the edge of the continental shelf and are pushed upward. This upwelling and mixing ensures that the waters around the Three Kings are cool and rich in nutrients year-round, but life has to be tough to take advantage of this mixed blessing.

Further turbulence is contributed by wind-generated waves and ocean swells that travel across hundreds of kilometres of ocean before smashing into the steep ramparts of the islands. Little wonder that the cliffs of the Three Kings Group appear so gaunt—mere wisps of vegetation cling to the highest slopes on most of the islands. And no surprise, either, that few boat trips make it to the islands, thwarted by rough seas and strong winds.

As a result, scientific study of the Three Kings has been small scale and piecemeal. This year, five agencies came together to add to our knowledge of the islands’ marine life in an orchestrated way by document­ing and collecting coastal fish, invertebrate and marine algae specimens during a 10-day visit.

The Three Kings Islands Marine Expe­dition aboard RV Braveheart comprised 14 people, including photographers and marine biologists from Auckland Museum, Te Papa Tongarewa, NIWA, and the uni­versities of Auckland and Queensland. We arrived at the islands at dawn in mid-April, in fine weather and with uncharacteristi­cally smooth seas. But beneath the super­ficial calm there was a hint of the constant underwater turmoil. The current was running at one knot; too strong for divers to swim against. Instead, tenders ferried divers close to the shore on the north side of the Princes Group of islands where we hoped to avoid some of the current.

We stopped in the lee of a sheer water-blasted cliff, close to an impressive archway. The islands are famously riddled with caves and arches, testament to the power of water to wear away rock over eons, and as we would discover over the next few days, many of these became impressive blowholes when the sea reverted to its usual pattern of big swells and pounding waves.

The first divers donned their equipment and began to descend as I waited on the bobbing inflatable with a mounting sense of anticipation. Would it be as good as eve­ryone had promised? And how would it compare to other prime New Zealand dive sites such as the Poor Knights and Kerma­dec Islands, where a number of us had dived on another biodiscovery expedition two years earlier?

Expedition leader Tom Trnski from Auckland Museum had explained that we could expect good visibility—the absence of soil on most of the islands in the group ensures there is very little sediment run-off to muddy the waters. But he also pointed out that just because the islands lie partway between the temperate Poor Knights and subtropical Kermadecs, we shouldn’t expect the marine life to reflect a halfway point between the two.

Rather, the Three Kings Islands are very much their own place, defined as much by absences as they are by a number of endemic species which reflect the islands’ long isolation from mainland New Zealand.

Although 53 kilo­metres can seem a long way in a rolling boat, marine larvae are capable of travelling many hundreds of kilometres. But despite this, spotties—a ubiquitous fish around the New Zealand coast—are absent. So, too, are mussels and blue-eyed triplefins. The famil­iar herbivorous butterfish or greenbone doesn’t occur here, yet the Three Kings have their own endemic species of blue-finned butterfish. The number of coastal fish species recorded from the islands is barely more than 100, yet a comparable piece of eastern Northland coast would be home to more than 200 species.

It was my turn to enter the water. I rolled off the side of the boat, and peered down. The cliff was as sheer underwater as it had been above, but in every other respect it was transformed. No longer bare, it was instead covered in a blanket of golden Sargassum that swayed gently back and forth in the ever-present surge. I could just make out other divers working nearly 30 metres below me, and as I began to sink towards them, I passed clouds of fish milling about the rock wall.

It was only when I reached the first fish-collecting station and began to intently survey the steep seafloor that the hidden world of the Three Kings was revealed. The main seaweed is Sargassum johnsonii, a Three Kings endemic often called totara weed for its resemblance to the foliage of the terrestrial tree. And exactly like large trees in a forest, the totara weed creates a strong three-dimensional structure that provides many microhabitats. I parted the forest canopy of Sargassum and underneath was a lush understorey, a riot of colours and textures. The stipes, or stems, of the Sargas­sum were covered in a profusion of minia­ture seaweeds, while the rocks below were a tightly packed kaleidoscope of sponges, bryozoans and ascidians, as well as an assortment of mid-sized red seaweeds­ some filamentous like fine lace, others with broad strap-like leaves, and still others that were thick gelatinous mats. Making their home in the shelter of this underwater forest were small fish; banded wrasse, half-banded perch and dwarf scorpionfish, many as bright as their surroundings.

Back on Braveheart after the first dive, clusters of excited scientists—still in drip­ping wetsuits—exchanged impressions and showed one another specimens. The stand­out topic of conversation was the Sargassum; everyone was struck by the spectacle of it. Marine algae specialist Roberta D’Archino explained that there were so many kinds of seaweeds, many of which she had only ever seen as photos, that she barely knew where to begin collecting.

As collecting bags were emptied onto white plastic trays, D’Archino and col­league Wendy Nelson from NIWA picked through the specimens closely, marvelling at the number of small seaweeds attached to the larger ones. Their conversation was punctuated by remarks about undescribed species and unknown family relationships. North-eastern New Zealand is the richest area in the country for seaweeds, with more than 400 of the 950 or so species that Nelson estimates for the whole country. She began the trip thinking that the Three Kings Islands were home to some 175 species of seaweed. But it wasn’t long before she was revising her estimate closer to 200—at least 14, probably more, endemic to this island group alone.

The invertebrate collecting team of Kareen Schnabel from NIWA, Severine Hannam from Auckland Museum, and PhD student Libby Liggins from the University of Queensland had the most challenging job. They were interested in any animal without a backbone, and many of the crea­tures they were keen to find were very small, impossible to find in a short period of time when the water is in constant motion. Their approach was to sample what they called the “substrate”—a representa­tive range of sponges, rocks, corals, whole seaweeds—and then wait to see what would emerge once they were back on the boat. For hours after each dive, the ‘spine­less team’ could be found patiently peering into trays of water, parting leaves with fine forceps and pouncing on tiny crustacea, wary worms and minute molluscs that were slowly emerging.

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The tops of all the islands in the Princes Group host New Zealand’s largest breeding colony of Australasian gannets, and long skeins of birds heading in and out to feed, and their constant calling, are a striking feature of the area. But alongside the gannets atop Rosemary Rock, the smallest islet of the group, roosts a colony very far from home. Buller’s albatrosses more usually breed on the Chatham and Snares Islands a long way to the south, yet in the early 1980s, an Offshore Island Research Group expedi­tion discovered a small number of the birds breeding here. Through binoculars, we could make out the albatrosses’ distinctive mud-pot nests, a few adult birds and some large grey downy chicks. Breeding clearly occurs here regularly, but the colony doesn’t appear to be growing.

After we had surveyed Rosemary Rock’s high slopes, our attention turned to what we knew lay below. NIWA’s Malcolm Francis had offered to lead photographers and the invertebrate team to a cave known as Catton’s Cave, at about 20 metres depth.

A fast current swept past the dramatic cliffs, but within the embracing shelter of the small cave was a veritable Aladdin’s grotto. Delicate, pastel-coloured gorgonian sea fans stretched out from every surface, covered in feeding polyps to filter plankton from the current, and often bearing a col­our-matched brittle star tightly curled around the fan waiting for the cover of dark­ness. The coral Oculina displayed an allur­ing colour scheme of ivory white with apricot polyps, while the rich orange heart of each large solitary cup-coral was offset by the vivid yellow sponge that encased it so perfectly that the two organisms appeared one. Bryozoans were delicate froths of pale pink or white and ascidians hung like bunches of slightly-wilted flowers.

Sponges made their own bold state­ments of colour and form—some like large black rocks, others fine structures of white organ pipes, bright-yellow bushes or big splashes of green and orange, as if someone had spilled tins of paint across the rock. It looked idyllic, but the scene was far from peaceful—space was at a premium, and eve­rywhere chemical warfare was taking place as immobile creatures fought their neigh­bours for territory, millimetre by millimetre.

Many sponges are rich in secondary metabolites, and it’s thought that some of these chemical by-products are used to deter other sponges and prevent them over-grow­ing. Further chemicals protect the sponge against microbial invasion, some prevent larvae from settling, while others produce unpleasant tastes and odours to deter animals that like to eat sponges.

But this defence doesn’t work on every grazer. Some nudibranchs—those gaudy little molluscs that have done without the protection of their shell—have evolved to dine on the toxic sponges, and others have even learnt how to concentrate the chem­icals they ingest to power their own defences, franchising the poison present in the sponges for their own benefit.

The living jewels in Catton’s Cave illus­trate the amazing structures that life can create in these rich waters when afforded some shelter. But back on the surface, we were about to experience what most marine plants and animals here already know. Out here there is nowhere to hide—no sheltered bays, no estuaries or harbours, just sheer rock walls, ripping tides and roiling waves. Before the storm hit, we left the Princes Group to find what shelter we could in the lee of Great Island, and over the next two days we came to appreciate that safe anchor­ages were transient affairs. The winds and swells kept changing direction, and so the crew of the Braveheart kept us moving.

Horizontal rain lashed at the boat and spray was whipped off the foaming surface of the sea. It was hard to see far, although occasionally we glimpsed enormous waves smashing into the cliffs in cascades of frothing spume, or bursting explosively from a blowhole. Everything was motion, and as we rose and fell on the backs of massive waves, water surged across the back deck and wind moaned around the ship’s superstructure.

Yet we were far from alone in the storm.

As we rocked and rolled, the seas around us filled with seabirds: at least four kinds of albatrosses in addition to the resident Buller’s, and a large contingent of black or Parkinson’s petrels.

Eventually, the storm blew itself out and, staying in the lee of Great Island to avoid the lingering swell, we began to dive and explore again. Every dive was different. The diversity of marine algae continued to amaze the biologists. We had glimpses of spotted black grouper, often hiding in a small cave or overhang, but they weren’t as large or as bold as those at the Kermadecs. That is, in part, because the waters around the Three Kings Islands are not protected. They’re frequented by sports fishers, and for most of the time we were at the islands, a cray boat was working its many pots. Yet there are good scientific grounds to consider giving at least some of the waters here protection to match the nature reserve status of the islands and their terrestrial biota.

By the end of our expedition, the team had gathered a wealth of specimens; some of them new records for the Three Kings Islands, all of which will be added to the col­lections of Auckland Museum and Te Papa to be identified and named. We left knowing that this resplendent Garden of Eden, so physically close yet so ecologically distant from the mainland, still holds many secrets, and will continue to offer up its treasure for all who care to look, to the benefit of marine science and our greater understanding of the seas around New Zealand.