Canyoning is not like caving or climbing. The term conjures wide, arid cliffs perched somewhere in the Arizona desert, rather than the narrow, flooded chasms it actually refers to. It involves descending through tight, often water-filled gorges using techniques such as abseiling, swimming, climbing and hours of arduous hiking.

Canyoning also isn’t a hybrid of spelunking (the American name for caving) and mountaineering. There’s a difference to canyoning that makes the experience of doing it more like skydiving; the knowledge that once you drop into that shadowy crevice, the only way out is down.

Two hours west of Sydney, amidst the sea of eucalypt that blankets the Blue Mountains, are some of the world’s most spectacular slot canyons, the deep, narrow gorges that canyoners chase. While most of these canyons remain completely unexplored, many of those discovered by avid canyoners are charted for less experienced adventurers to explore without the need for expert navigation.

The locations of even popular canyons are mysterious. Though this might seem to be due to selfish veterans or even attempts to preserve these pristine examples of primordial nature, a big part of canyoning is discovery and exploration. The disclosure of new canyons is therefore frowned upon – it would deny others the same, all-important privilege.

It’s these remote and uncharted slots that present the ripest opportunity for adventure, but carry an elevated risk of canyon-related dangers. Aside from the obvious hazards, such as falling off a waterfall, canyoners are at risk of breaking an ankle in a pool of water so clear and motionless it might be mistaken for thin air, or drowning in flash floods that can submerge narrow caverns in a matter of minutes. More commonly, however, canyoners find themselves hopelessly disorientated after losing their bearings in the labyrinth of intersecting valleys and repetitive landscapes.

One such slot, the aptly named ‘Claustral’, so named for its confined, claustrophobic passage ways, is widely considered by canyoners to be one of the most spectacular and technically rewarding in the world. Its first set of waterfall descents drop the abseiler into the inky-black void of a water-filled cave. Then after crawling through a narrow opening known as the Black Hole of Calcutta, and descending deeper still into the darkness of the cavern, the canyoner is rewarded with chasms illuminated by shafts of white sunlight breaking through prehistoric ferns and streaming down the damp, narrow ridges of the canyon, and fractures of fertile green sprouting from the moist, black walls and collapsing into cracks of limestone as they reach toward the canyon floor.

Canyoning, unlike a majority of thrill-seeking pursuits, offers a reward for your efforts beyond adrenaline. More than anything, canyoning is journey into ancient, unspoiled nature. A world hidden away from those without the nerve or curiosity to plunge into these dark, twisted cracks in the earth.

Anyone canyoning in this area is encouraged to contact the local police to report their whereabouts and get an emergency distress beacon. More importantly, anyone canyoning for the first time should contact a local adventure company or professional before approaching unmapped or advanced slots.