Abseiling through a pitch black abyss in a dank seven-degree Celsius environment while wearing a plastic suit and 10 kilograms of equipment does not make for a relaxing weekend.
But relaxation is far from the priority for a group of eight cavers hoping to confirm that Australia has a new deepest cave.
After six months of challenging preparation, the group from the Southern Tasmanian Caverneers, a speleological organisation based in Hobart, will head underground over Saturday and Sunday, hoping to make the discovery.
Caver Ciara Smart is one of the team.
"We're hoping to make a connection between a cave that we discovered in January and the existing Niggly cave system," she said.
"By making this connection, we're going to break the Australian caving depth record by taking it over 400 metres for the first time."
Niggly Cave is Australia's deepest known cave at 397 metres, near Tasmania's Mount Field National Park.
Its record depth was confirmed in 2019 when cave diver Stephen Fordyce connected a guideline from the Growling Swallet system to one in Niggly Cave, proving they were linked.
The STC has been working to try to confirm their suspicions that another slightly higher entrance to that system, known as the Delta Variant cave, also connects to Growling Swallet.
That would mean the Delta Variant cave was more than 400 metres deep, making it Australia's new deepest cave.
The discovery is due to a decades-long project to map the region's caves, involving years of searching data and maps for clues and plenty of hiking through the wilderness looking for holes in the ground.
"We know that we're going to break through to Growling Swallet because from the Growling Swallet/Niggly system is a big waterfall coming in and we've been walking around at a face level in this system, looking up at this waterfall for years, wondering, 'where does this water come from?'," Ms Smart said.
"In January, we found the source of this water, which was a creek flowing through the bush on the surface and so we've spent six months following this water down through Delta Variant, along all these abseils and we're finally going to come out in Growling Swallet.
"The funny thing is, the entrance to Delta Variant is only a couple of metres away from the entrance to Niggly, so we spent 30 years walking very close to the entrance without finding it."
Cave's internal features named after pandemic
Over six months, they have been slowly roping more and more of the cave in their attempt to connect the Delta Variant to Growling Swallet.
"Each trip we're limited in terms of how many ropes we can carry because they're heavy and there are squeezes and only so many people," Ms Smart said.
"So each trip we go down into the cave carrying quite a lot of rope, fix that rope, head down that rope survey — using our mapping technology — and then go back up the rope, put all our information into the computer to produce a map and then think about the next trip where we do it all again."
In a nod to the times, the Delta Variant cave's internal features have also been named after the COVID-19 pandemic, including the Quarantine and Daily Cases abseils and the unmapped areas Superspreader Section and Vaccine Strollout.
"It's a highly vertical cave, so we're lucky in this area of Tasmania, a lot of our caves are very vertical because they're formed by water slowly dissolving the limestone," Ms Smart said.
"That's quite challenging to negotiate because, as you can imagine, it involves a lot of abseiling and in between the abseiling there's a bit of squeezing, sometimes a bit of walking.
"It can require quite a lot of acrobatic movements to negotiate."
Dangling from a rope 'higher than tallest part of Sydney Harbour Bridge' — in the dark
The largest abseil in Delta Variant is 153 metres.
"So that is higher than the tallest part of the Sydney Harbour Bridge, if you can imagine what it would be like to abseil from the top of the bridge to the water in one go without getting off the rope," Ms Smart said.
"But it's extra intimidating because you can't see the bottom of the rope because everything is dark in the cave, there's no light."
Ms Smart said the exploration process had been exciting because the team did not know what they would find.
"You get to the edge of a cliff in the cave and you look down and you can just see this huge black abyss below you," she said.
"Which is a pretty exciting moment for a caver to know that you're standing on the edge of something that no one has ever seen before or even knew existed, there's no other feeling like it."
The cave is also wet and cold.
"If you get quite cold then you pretty much have to exit the cave, so we have to manage our temperature all the time," Ms Smart said.
"Just moving through a cave that nobody's ever been in before, you never know what you're going to encounter, what sort of hazards you're going to encounter. So it's all quite slow and safe and careful, as much as we can manage."
The cavers are hoping to confirm they have made the connection on Sunday.
