As the helicopter heads into a bank of thick cloud, we are both excited and apprehensive. We know that towering cliffs surround us and below lie the cold, deep and dark waters of our destination; Tamatea / Dusky Sound. It is hidden amongst the clouds in Aotearoa, New Zealand‘s far southwestern corner. Getting here takes two days, involves planes, rental cars, a helicopter, and finally a boat. It’s a cold, wild, rugged place with soaring cliffs that plunge to over 300 metres depth underwater. The top layer of water is an eerie tannin-stained, uninviting brown. To say we’re apprehensive about donning our scuba gear in the cold, pouring rain, and jumping into the frigid waters is an understatement. We just have to keep reminding ourselves that this place is like no other, one of the last truly wild places in New Zealand. We’ll see deep sea creatures in shallow water and witness a place where time stands still, or at least it should.

Fiordland National Park is a wilderness consisting of 14 fiords carved by massive glaciers about 20,000 years ago. These glaciers shifted rocks to the seaward entrance of the fiords, which to this day, still shape the dynamics of the marine realm. Although most of the fiords are between 200-400 metres deep, the glacial deposits narrow the fiord entrances and restrict the water flow in and out. In the northern fiords, the circulation of water is confined to the top 20–40 metres and deeper waters may remain undisturbed for years. The longest of the fiords stretch 40km inland and they become wider, the mountains lower and less steep as you travel south. According to Māori legend, this latitudinal change was due to the increasing skill of the god Tu Te Raki Whanoa. He began forming the fiords from south to north becoming ever more practised as he carved the majestic and towering walls of the northern fiords. By the time he created Milford sound, the most northern fiord, he had perfected his technique. Nowadays, Milford sound’s sheer cliffs, thundering waterfalls and mountains are still considered some of the world’s most unique geographical wonders.

It is not only the geological history and location that make Fiordland unique as the weather shapes the landscape and ecology above and below the waterline. In Fiordland it rains on average two of every three days, with over 7 metres of rain falling annually. In 1773 on Captain Cook’s second voyage to Fiordland, he even named a section of Dusky Sound ‘Wet Jacket Arm’ after his boat crew got stuck in a torrential downpour while exploring the area. Although the rainfall may dampen the spirits of humans who venture into Fiordland, it also nourishes the temperate rainforest clinging to the hills. The rain runs down the steep cliffs creating hundreds of waterfalls as it cascades into the fiords. Tannin-stained from the leaf litter in the forest, the yellowish-brown freshwater forms a layer up to 15 metres thick on top of the more dense and clear seawater. This layer filters out all but the green light wavelengths, creating an eerie, dark green world below.

Having heard for many years about this unique corner of New Zealand, we were excited to join our first dive expedition to Dusky Sound deep in the heart of Fiordland. Armed with information from some of the scientists we work with about the best and most hidden treasures, we embarked on the two-day journey down the length of the country. After a 2-hour car ride, 3-hour flight, and a 2.5-hour shuttle bus ride we reach Te Anau, a quaint town just east of Fiordland National Park. It’s freezing and pouring down with rain, which is not unexpected in southern New Zealand in the middle of winter. Our small team of eight explorers spends the night chatting excitedly about our trip, worrying about how the pile of camera and dive gear will fit into the helicopter tomorrow, hoping that the torrential rain and thick cloud will lift for long enough for us to get to our destination over the towering mountains.

In the morning, to everyone’s relief, the mountain of gear does fit, even though some of the food supplies are packed in around us on the seats. The rain doesn’t abate, but the skilled helicopter pilots somehow manage to weave through a gap in the clouds to deliver a slightly shaken group of divers to their destination. We land on the ‘Uni’, a derelict barge that acts as a helipad, a warehouse for commercial crayfish gear, and a wharf facility for the charter boats working in Dusky Sound. The MV Pembroke, our floating home for the next week is tied up alongside, and we form a chain in the rain to get our gear onboard. The next morning, we wake up to sleet and the view of a gigantic waterfall out of the galley window. As our skipper gives us the ‘20 minutes until the dive’ warning, we hesitantly shuffle outside into the cold to gear up. As we enter the water, the cold takes our breath away and we must trust the process as we descend through the inky freshwater layer.

Moments later, at about 6 metres depth, we drop through the halocline and burst into a crystal-clear view that resembles another planet entirely. Off to the left, over 30 metres below, we can see the faint glow of the other divers’ torches and as we spin around to find our other buddies, we come face to face with a black coral tree, usually only found in waters well over 40 metres depth. Professor James Bell, a researcher at Te Herenga Waka – Victoria University in Wellington, spends most of his research hours underwater in Fiordland and still marvels at the diversity. With a grin on his face, he explains: “One of the things that is so special about underwater communities in Fiordland is the dense animal- dominated forests that usually occur at depths beyond those most scuba divers can reach. Because of the limited light penetration, seaweed populations decline quickly with depth and the rocks become covered in animals including sponges and massive black corals, some of which are hundreds of years old.”