A team of passionate adventurers who have spent more than a decade exploring the Bisaro Anima cave near Fernie are now the subject of new documentary called Subterranean, which is showing at Banff Mountain Film Festival on Nov. 4

The film, released in April, follows multiple groups of explorers who are seeking to break caving records. The group in Fernie, lead by Katie Graham, beat a personal depth record by ascending further into the Bisaro Anima cave network than ever before.

Bisaro Anima is located along Heiko鈥檚 Trail. It is the deepest cave in Canada and the continental U.S.

The team climbed up steep rock faces, crawled through claustrophobia-inducing tight spaces and explored cold damp caverns. Parts of the cave network were underwater. Graham reached her depth record by scuba-diving through these.

鈥淚t鈥檚 cold. It鈥檚 dark. It鈥檚 drippy all the time. Everything鈥檚 covered in mud. It鈥檚 quite extensive, so it changes character as you go. Sometimes you鈥檙e crawling and then sometimes there鈥檚 these massive chambers. You鈥檙e rappelling down 100-metre-long pits. Sometimes the rock is really unstable,鈥� said Graham.

Graham had to complete scuba training in order to navigate through the cave waters.

鈥淵ou only see what you can shine the light on,鈥� she recalled. 鈥淚t鈥檚 absolutely dark. The water鈥檚 really cold and once you go in you鈥檙e just completely on your own. You have to be 100 per cent self-sufficient and confident.鈥�

鈥淵ou really have to be hyper-focused on the technical aspect of what you鈥檙e doing, and you鈥檙e trying to be aware of your surroundings. There鈥檚 so many risks and you鈥檙e trying to manage them and keep yourself in a really positive and systematic head space, going through checklists and make sure you鈥檙e doing everything right. You really have to keep yourself grounded.鈥�

The film was lead by Vancouver film producer Jenny Rustemeyer and director Fran莽ois-Xavier De Ruydts. The film crew accompanied the team into the cave on a number of trips, sometimes for as long as nine days, and they all slept in the cave overnight.

De Ruydts reports that it was a challenging film to make. Filming without much light and no access to power was difficult, he said, and he had to be strategic about his filming to ensure he had enough power in his equipment to last the entire trip. Special equipment was required in certain areas of the cave network. When Graham went underwater, she was filmed by a drone.

It was rewarding nevertheless.

鈥淎round every corner, you鈥檒l find something fascinating because it鈥檚 so different from what you鈥檝e experienced before. Just darkness. You turn off your lights and it鈥檚 black 鈥� All the cave formations. There are stalactites and stalagmites,鈥� he said.

The cave was only a few degrees above zero, with intense humidity. It was also wet and the crew had to wear their damp clothes to bed in order for them to dry by morning. They slept in covered hammocks to keep themselves warm.

鈥淵ou have to go to bed with your wet stuff. Otherwise, in the morning, it鈥檚 still going to be wet. The only way to dry stuff is to wear it. Usually sleeping in it is the easiest,鈥� De Ruydts said.

Subterranean has reached screens across the world, and more local audiences through Fernie鈥檚 Vogue Cinema, which showed the film on Oct. 6. The film will premiere on Knowledge Network on Nov. 7 in British Columbia.

De Ruydts said caving represent a niche corner of the market among adventure documentaries.

鈥淧eople usually come to see mountaineering or climbing 鈥� It鈥檚 refreshing on the festival circuit because it鈥檚 different,鈥� he said.

Graham said the team hopes the documentary will give more exposure to the sport of caving and the science behind it. They鈥檝e been scientifically investigating Bisaro Anima since 2012 and have published a survey of the cave, which they continuously update as they gather more information.

鈥淪eeing the movie come out and seeing it well-received, that鈥檚 actually really nice,鈥� she said. 鈥淭he goal was really just to make the science and sport of caving better-understood. Having that positive reception on the movie feels great.鈥�

It was only just a week ago that the team made a new discovery 鈥� a circular tube-like passage that provides clues about the climate during the Ice Age.

鈥淲e found a passage that is a five meter wide diameter circular tube with lots of scallops in the wall. What that tells us is that there was an incredible volume of water with a glacier on top that was just pushing an incredible amount of water through that mountain,鈥� she explained.

鈥淭here鈥檚 already lots of theories, hypotheses about what the general climate was like [during the Ice Age] and you can use the cave as proof for the micro-climate for that very particular area. You can get evidence to help support those bigger theories.鈥�

The group has explored approximately seven kilometres of cave network and plunged over 600 meters deep since they started their research, but they still haven鈥檛 found an end yet. Graham said they鈥檙e certain there are more dry passages beyond the body of water that she scuba-dived through, which they haven鈥檛 been able to reach due to oxygen limitations.

They鈥檝e also found bushy-tailed woodrats in the cave in really deep areas, which tells them that there are entrances to the cave they haven鈥檛 found yet.

Graham plans to continue her training in Mexico with specialized equipment, so she can dive even deeper next year.

鈥淎s it gets technically more difficult, it challenges me to up my game and do more training and get better. It made me focus,鈥� she said.

鈥淵ou kind of feel like you鈥檙e travelling back in time and you鈥檙e trying to figure out what the story is behind it.鈥�

READ ALSO: VIDEO: Cavers embark on new expedition to Canada鈥檚 deepest cave in interior B.C.

READ ALSO: B.C. man reflects on caving drama as soccer team still trapped in Thailand