It's been one month since two Australian divers risked their lives to assist in the international rescue of a Thai football team. Now, Craig Challen and Richard Harris take the plunge into their first dive with their mates since those dramatic events.
In a paddock in regional South Australia, a group of mates reunite to share their combined love of a pursuit some might find hard to understand.
An unsuspecting passer-by would never guess what lies beneath the ground here, accessible only through a small rectangular hole hidden next to a cabin.
Today, it is the meeting place for the Wet Mules, a diving group flung into the international spotlight when two of its members were called upon to help with the rescue of a Thai soccer team and their coach.
Two of the Mules, Craig Challen, a retired vet, and medical specialist Richard Harris, have helped to map underground caves around the world, including this one — Tank Cave — near Mount Gambier.
For Challen, the chance to meet up with the Mules and other diving mates to explore an old stomping ground marks a return to normalcy after being placed firmly under the international media spotlight during the Thai cave rescue.
"It's definitely a lot colder here than Thailand, rain's about the same," he jokes.
"We're getting back to normal life, we've had our big adventure."
But the adventure, it would seem, only continues.
Tank Cave — known as the "crowning jewel" of the southeast — is one of the longest underwater caves in Australia.
While outside the cave looks simple enough, underneath the limestone bedrock lies an extensive, maze-like system with more than seven kilometres of underwater passages known to professional divers.
They prepare just like they do ahead of any dive — starting with pulling on diving gear, mapping their journey and making sure everything is in good working order.
"It's not something where things are going to come out of left field and surprise you," Challen says.
"They're not the problems that cause accidents — it's more lack of preparation, the gear not being prepared, lack of experience, so if you have everything well sorted before you start the dive, then generally everything will be okay."
Preparation is not the only lucky charm.
Colin — the club's bowling ball mascot — was found by Harris in a volcanic sinkhole in Queensland.
"We thought he looked like our type of guy, he's been with us ever since," Challen says.
"He's a real doer, Colin, he's into it."
Next to the shack, the team climbs down a steel ladder into a small concrete hole, entering a small underground room where they put on their masks, strap on their two air tanks and do the final preparations.
At the end of the room a small freshwater pool drops eight metres down into Tank Cave, and that's where the real adventure begins.
It might look like an open space, but over the course of the next two hours, the divers move through tunnels and squeeze through small holes to explore the nooks and crannies of the cave, some opening to underwater rooms up to 10 metres wide.
At first, the cave water is clear, but in small, tight passages, disturbed silt can reduce the cave to zero visibility.
It's one of the elements that made the Thai cave rescue so challenging.
Challen says low visibility is where the permanent fixed lines placed along the inside of the tunnels come into use, with divers moving their hands along them to guide them through the cave system.
For some, exploring the depths of the tunnels is a form of meditation.
Mules member John Dalla-Zuanna compares the feeling of cave diving to being in a flotation tank.
Divers focus on calm and deliberate movements through the water to not disturb the silt.
"I just feel at home in a sense. It's just gliding weightlessly through space. I just love being weightless and all I'm hearing is my breathing. I can sort of feel myself in tune [with] the water," he says.
"You've got no phones, you got no pressures about what you do at work … and we've driven four to five hours in each direction to get to here and all that stuff, that all goes away.
"We come here on a weekend and we come here for the sake of experiencing something like this."
For others, Tank Cave is akin to exploring space.
"Lots of people suspect the area is criss-crossed with caves waiting to be discovered but it's a matter of discovering them," diver Tim Corbin says.
"There is one below us but there might be one in the next paddock.
"At the beginning the cave behind us was under a water tank and the entrance into it was a little muggy hole so I imagine for the early adventurers it would have been really like going into space I would say."
The rope lines fixed to the sides of the tunnels are one of the elements that have helped to bring greater safety to cave diving.
The Cave Divers Association of Australia was formed in 1973 following a series of deaths in caves and sinkholes in the Mount Gambier region.
Dalla-Zuanna is also the association's standards director, with a focus on techniques needed to stay safe while exploring caves.
"In this particular game we use redundancy as a big tool as part of our risk management strategy. So we have two of everything; we use two masks, we have two complete scuba units, we have two cutting devices, we have multiple reels," Dalla-Zuanna says.
"We have the equipment so that we are self-sufficient and, if something goes wrong with one part of our equipment, we have a second piece of equipment that we can go to."
While it's much safer that it once was, lives have still been lost.
In the same cave, two experienced divers, Agnes Milowka, 29, and a Victorian man, 40, died in separate incidents in 2011.
Milowka, who worked as a stunt diver in the James Cameron movie Sanctum, died in a narrow passage after separating from her diving buddy.
Harris — not for the last time — was called on to help, with the heart-wrenching responsibility of recovering the body of Milowka, his close friend.
But it's the enduring friendship and camaraderie that keeps the Wet Mules coming back to the site.
For them, it's a way to come together to dive with trusted mates and unwind from the bustle and stress of everyday life.
"When you're young and inexperienced you do get yourself in a few sticky situations that you've got to extract yourself from," Challen says.
"You're really on your own even if you're in company underwater so you've got to be able to depend on yourself."
The group's name derives from the phrase that a wealthy man has "enough money to burn a wet mule".
"That was all just a bit of a joke really — we had a delayed flight in Christchurch, New Zealand once," Challen says.
"We were sitting in an airport for six hours and just talking about ridiculous things and we made this group and thought of a ridiculous name, and away it went from there."
Challen — a cave diver of 24 years — says he is "way past" feeling nervous each time he descends into the deep, dark waters of a cave.
So, why does he do it?
"We do have a saying that if you need to ask that question, you wouldn't understand the answer," he says.
- Photography: Tony Hill
- Underwater videography: Chris Edwards
- Producers: Rebecca Puddy, Jessica Haynes and Daniel Keane
- Video production: Nathan Cross and David D. Stuart
- Thanks: Tim Leslie, Matt Liddy, Christopher Moon and Michael Coggan