Deep, dangerous and unseen

We are walking through the forest, along the ancient tramway where bullock teams once hauled the timber used to build colonial Hobart. Here and there, ghosts are visible through the undergrowth: we see a collapsed brick wall covered in moss; an old beer bottle, half buried in the forest floor; a giant tree stump, notches cut by the rough hands of convicts. Ferns reach out from the overgrown verges and brush our faces with the rain clinging to their fronds. My pack, filled with lead weights and diving equipment, pushes me down into the muddy hollows that will one day fall through to join the giant cave system beneath our feet.

Loggers were the first Europeans to find these caves at the base of a cliff where the stream disappears into darkness, carving a channel through the limestone to the shattered rock at the foot of the mountain. Leaving the friendly, sun-dappled ferns and sassafras-scented forest behind them, they followed the tannin-stained river down into the cold damp stone. Exploring by touch alone is unusual for humans; we are so reliant on sight. But, once adjusted, these early explorers’ eyes were rewarded with the most amazing spectacle: colonies of glow-worms, thousands strong, creating constellations and galaxies within the pitch-black universe of the cave. A galaxy is an apt description of the cave environment, cut off from the outside world by unique conditions, geographically and geologically isolated from other cave systems that each have a unique cast of creatures. 

One hundred and fifty years after the first visitors to the southern caves, we approach in the same spirit of exploration as part of a survey team mapping more than 25 kilometres of tunnels, some of which no human has ever gazed on before.

One of many smaller water-filled passages that branch off Exit Cave’s main waterway

“It’s a voyage of discovery, really,” Exit Cave survey coordinator Tony Veness told me over lunch once. “Where other people have been and left notes saying ‘too wet, too low, too hard, too high’, it’s always tempting to say we can do better.” 

Caves are one of the least explored areas of Earth, and even in caves that are relatively well-known such as Exit Cave, there are new areas being discovered. “Last year we found an area we called Hardman’s Way. It’s just off the main drag. We were in search of where the river went from a large rock pile. Three of us went in search of it, plopped back into the stream – which probably no one had ever seen before – and off we went. We came back this year and all of our survey stations were still in place. We sketched it and tried to push through the end of the tunnel, but unless you had a rat on scuba you wouldn’t get through.”

Veness is already deep underground and several kilometres ahead with another team when we reach Exit’s mouth. Like the animals inhabiting the cave, we have to adapt to the darkness. Changing into boiler suits and miners’ helmets, we stow equipment in waterproof trog packs and make our way from the mossy boulders at the mouth to the entrance of a small tunnel. We crawl 200 metres along the low, narrow, muddy crawlspace that’s home to thousands of cave crickets and their nemesis, the Tasmanian cave spider.

As we enter the main passage the shadows cast from our head torches become steadily larger with the growing tunnel until they are giants standing inside a cathedral-sized cavern, the darkness at the far end out of reach of even our most powerful torches. 

We move to a point where a smaller passage splits from the main river. This is why we are here. This is Janine's dive site.

Janine McKinnon started cave diving in New South Wales in the 1970s, at the time the Cave Diving Association of Australia was in its infancy. “There was no training to do, so we trained ourselves,” she says, talking matter-of-factly about one of the most dangerous sports in the world. It begs the question why? “The exploration is always a big draw," says Janine. “I just like going to those places and seeing them, and when they’re not visited very often it becomes even more interesting. I’m in this place and nobody’s been here.”

The caves in Tasmania are some of the wildest in the country. “In the south we have the deepest, wettest, coldest, most spectacular sporting caves. We have the most highly decorated, beautiful caves in the country by far.” Many of these caves have vertical entrances, are geographically isolated and are not even detailed on maps. Exploration, therefore, is difficult. Then there is the danger. “When you’re down the bottom of a cave here and you’re miles from anywhere and there’s no other divers, you do know that if something goes wrong, they’re not going to rescue you. They are going to have a lot of trouble even getting someone to go in and get your body out.”

Our team splits in two at the junction, parting ways to survey different areas. We enter the side passage as support for Janine’s dive. The passageway is waist-deep with freezing water and car-sized boulders. We wade through, carrying some of the diving equipment and camera gear. The low roof gives us a close-up view of glow worms that in the higher caves seemed like distant galaxies. The tiny fly larvae suspend themselves on silken hammocks, casting threads covered in droplets of sticky mucous to catch flying insects that are attracted to their pale glow. The slightest movements that we create in the air when we pass by send hypnotic ripples through the fine threads, normally safe from tangles in the breezeless cave. 

Caving is inherently dangerous. In this cave system in 1990, three people died when a school group was caught underground by flash flooding. It’s something I reflect on as Janine performs some last-minute checks of her equipment and her husband Ric triple checks her double checks. Cave diving is technical. Janine tells me, “Even your backup equipment needs to be backed up, especially when diving alone.” It's something that many divers consider almost suicidal. With final checks done, Janine poses for a photo and sinks below the surface and into a tunnel that will lead her to unexplored areas of the cave system, and hopefully to the outside, where the river first sinks below ground. 

Descending into Exit Cave

. . .

We pack up our gear and leave. Ric decides to take us up the main river passage and into a cavern called “the ballroom”, presumably to take his mind off of his wife, who is currently swimming upstream in an airless, murky river passage. In contrast, our surroundings are spacious and several stories high, with delicate cave coral and millennia-old flowstone decorating every surface. Our torches sweep across the terrain and the light is reflected off a frosting of tiny crystals, billions in number, creating the illusion of freshly fallen snow. 

The entrance to the ballroom is a squeeze through a narrow gap between small stalactites. Ric points out the need for cavers to be aware of these delicate structures that are easily broken and take thousands of years to form. One bony finger of stone sticks up, uncomfortably tickling my ribs as I slide through. Inside, a solid limestone ball the size of a grapefruit is suspended from the ceiling by a cave straw, one of the long, thin, hollow limestone tubes that hang from above and give the area its name. 

We stop for photos and I notice a cave harvestman, a harmless relative of the spider, close to my knee. In Tasmania the above-ground variety are known as “daddy longlegs”. The name could also apply to the below-ground variety, as the cave harvestman’s extraordinarily long thin legs help it find its way in the darkness, where it can search for months before finding food.

We explore the area for several hours and head back to the dive site to see if Janine has surfaced. She didn’t make it to the outside on her dive, stopped by a rock fall where part of the cave ceiling had collapsed. She did get a little closer to linking the two ends of the tunnel and became the first person to explore this small section of cave. She told me that the other side is also blocked and she thinks that it might be due to the same rock fall. There are 15 to 20 metres of passage to find that connects the outside and inside tunnels, but that will have to wait for another trip. 

The cave environment is a stark contrast to the lush forest outside 

There is no money to be made by exploring Tasmania’s wild caves. There are only discoveries to be made. Exit Cave doesn’t give up its secrets easily, but almost no exploratory party that goes into Exit leaves empty-handed.

Many Tasmanian cave systems are freely accessible to the public, but Exit is one of a small number of caves which are closed to all but experienced speleologists because of their sensitivity to damage.

Photography by Jonathan Esling and Ian Stewart

Fraser Johnston is a filmmaker and Emmy-nominated Director of Photography based in Hobart. He specialises in natural history, science and documentary storytelling. He works commercially under the name Spectral Media and has worked has worked on broadcast productions for National Geographic, Netflix and Terramatter, as well as numerous online short form films and factual web series. Find Fraser's work online at and follow him on social media @Spectralpics and Spectral Media.

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