Caving doesn’t appeal to everyone but, unlike school netball and rounders, it is exciting, invigorating, messy, and pretty much rule-free. Success doesn’t depend on being selected for the team; it is an individual thing, yourself against Nature and Nature doesn’t care whether you live or die. I thought about that often, serving as a cave rescue warden. Caving satisfied my life-long need to prove myself, and show that women can be as intrepid as men.

I sought out new challenges and decided to push the limits with a round trip within Mendip’s longest cave system. Rising at a high point in Somerset, a river mysteriously disappears in the middle of a farmer’s field and then crashes and booms through six miles of passages until it joins other subterranean rivers in Wookey Hole. Eventually, it emerges as the River Axe near Wells. Most visitors to Swildon’s Hole follow the river down through the cave until the roof comes down so low that continuing means diving through an underwater passage – a sump. Few go any further.

The trip I wanted to do involved free-diving, not just this one, but three flooded passages in all. I am a strong swimmer and, in a pool, can manage a length underwater so although the longest sump is 33ft and rated ‘difficult’, I thought I could do it. I knew the first person to have free-dived this sump. He was a cave-SCUBA-diver. He hadn’t planned to do any free-diving but found himself on the wrong side of the sump having used up all his bottled air. Being the first earned him the nickname of Fish. When I talked to him about attempting it, he was discouraging but perhaps he didn’t want his achievement eclipsed through being repeated by a mere woman.

Together with John, a regular caving partner, I donned battered wet suits, climbing boots, helmets and miners’ lamps and scrambled awkwardly down between a collection of slick black boulders. Soon though we could stand upright and follow clear bubbling water down a series of beautifully sculpted corridors decorated by gleaming white stalactites and translucent calcite curtains. Oddly caves don’t seem like dark places because helmet-mounted lights ensure that everywhere we look is brightly lit, until things go wrong.

At weekends the first part of the cave can be crowded with less-experienced adventurers. The Forty Foot Drop is often a pinch point. Here the clear stream looks like a salmon river as it powers over a sheer edge and rumbles away into the depths. Most cavers descend the drop using a portable steel and wire ladder, but we’d discovered routes to free-climb this particular impediment. We moved between shivering boy scouts while John, chatty as ever, said chuckling, ‘Did I tell you? I was called out by the Police last Sunday night. Two young lads had gone into the cave with black rubber torches and hadn’t come out. The batteries had died after a couple of hours, no doubt. The boys were here, quivering with cold, at the bottom of the waterfall. I threw down the safety rope and shouted, ‘Tie on! Then climb the ladder.’

‘I heard from below, ‘Where do we tie the rope?’

I wanted to get back to my pint and shouted down my reply, ‘Where do you think? Round your fucking neck! After a bit of faffing, I finally felt the rope give as the first boy climbed up. His head appeared over the lip of the waterfall and – I’m not kidding – he had the rope tied around his fucking neck!’

 ‘Seriously!’ I said, ‘You couldn’t make it up, eh?’

I slid over the edge of the waterfall. I found a jug-hold out over the drop, felt with my feet until they found a ledge and swung in through the sparkling water. Once under the cascade, a series of easy moves got me to the bottom. Meanwhile long lean John had straddled the little subterranean canyon and danced down the rockface like Spiderman.

Invigorated, we splashed on through ankle-deep water, our boots crunching on ivory-coloured pebbles and pieces of calcite crystal. We jogged along corridors with walls made of fossil seashells and coral. While John expertly climbed down the Twenty-foot Pot, I ran my fingers over the strata and flowstone formations that looked like icing. Everything was so pristine I wanted to stop and admire the wonderful patterns in the rocks and a pool of cave pearls.

The next landmark was the Twin Pots where double waterfalls dropping 15ft or so have rattled boulders around in circles to form two perfectly round bath-tubs. Two young men were edging around the rims of each pot but we knew that the water was free of boulders and only chest deep so, exuberant still, we jumped in with satisfying whoops, splashing both lads. This was Type One fun.

Laughing still, we separated. John was an excellent caver and, unlike me, was cool climbing sheer rock-faces, but he definitely wasn’t keen on water so I left him to continue down the main channel to Sump 1 where he’d wait for me. My route now involved a meandering climb above the river, taking an unfamiliar direction that circled around and above this first sump to rejoin the river perhaps half a mile downstream. Then navigating upstream again I would need to negotiate three submerged passages before I met up with John again.

I scrambled up into higher passages that were seldom river-washed: there was more mud and less shine but I felt intrepid. I liked being totally alone for a while. I especially loved visiting places few others had been. After the next big scramble, I sat to get my breath back, raising my own personal steam-clouds with each exhalation. I switched off my light to absorb the strangeness of total blackness.

Eyes wide open, scanning this way and that, there was not even the subtlest of shadows. Nothing. Not a glimmer. Nowhere on the surface of this planet can you experience such a total absence of light. In such absolute blackness the mind hallucinates sparks and shapes.

I recalled a friend whose light had failed and he tried to navigate using occasional flashes from his camera but although the flashes lit up whole chambers he couldn’t navigate these images in his mind as he tried to move through the cave. Eventually, bewildered, he sat and waited until we rescued him. Another friend did manage to find his way back to the cave entrance just by the orange light of a cigarette. With his eyes accustomed to blackness, dragging on the cigarette allowed him to see the details of the chambers and corridors he was moving through.

I listened in the blackness. I was too far above the river now to be able to hear it, or anything going on in the world above. There were subtle sounds of the cave breathing. There was perhaps a distant flutter of bat wings. Otherwise, there was only the slow drip, drip, dripping as drops collecting in cracks in the cave roof or on the tips of stalactites fell into pools or onto rocks. This was true sensory deprivation.

I shivered. My butt-cheeks were numb. Cold was seeping into me. I checked my emergency glow-stick was still safely tucked up inside my wetsuit near my calf, switched on my cap-lamp and headed onwards.

Maybe half an hour later, I heard the river again. I’d arrived in a medium-sized chamber at the top of another descent. Others had described this landmark, and it was good to know that I was on track. This drop was 15 or 20ft but at an angle of only about 30° so going down should have been easy. The surface though was a water-smoothed slab of limestone that was covered with cave-clay. It was soap-slippery but I wasn’t going to edge down on all fours.

I was all-too-aware of the danger even of an ankle sprain this far underground. Hypothermia soon sets in and people die but I was exhilarated and threw caution to the wind, launching myself with a manic shriek, which echoed back at me as I joyously hurtled down the face of the slab. I’d started to slide feet-first but spun on the descent so rejoined the river below with a spectacular but inelegant splash. I was still laughing and feeling slightly dizzy as I scrambled to my feet. I registered a slightly bruised left buttock, but was pleased to have reached the main river again. I turned now to head upstream.

It wasn’t long before I reached the first of the three sumps I’d need to swim. This, Sump 3, was the one rated ‘free-divable but difficult’. This was the one Fish had discouraged me from attempting, and now I was here, 33 feet was indeed an intimidating distance. I was determined though. Maybe I’d be the first woman to free-dive it.

As expected, there was a decent-looking rope tied via to a bolt in the rock at my end and I pulled to check that the other end was secure too. Churned up sediments would stop me seeing much – if anything. Nor did I know if there was scope for turning around if anything went wrong.

There was no point in thinking too much about this though. That would only make me feel even more anxious than I already was. I took steady breaths and then a really deep one and plunged in.

My helmet clattered against rock. My wetsuit made me too buoyant, sticking me to the uneven cave roof. I felt for the battery at my waist, checking. I tried pushing off the rocks with my boots but that didn’t help. This wasn’t going to be a smooth easy swim. I thrashed. I struggled to unpeel myself from jagged protrusions in the cave roof. Then, finally, I settled for pulling myself along the rope while on my side, fending off the roof with my elbow. I still crashed into rock a lot but I was making progress – not good progress, but some progress.

How far had I gone? All I could see was a mud-coloured blur. My helmet rattling on the cave roof made a lot of noise. I needed to get to air soon. Maybe I should turn back.

There was supposed to be an airbell part way but could I find it? Or was that in the other sump? Best continue. I pulled and pulled. I had a feeling I’d put my fist up into air but wasn’t sure. I pulled and concentrated on nothing but that. My need to breathe was becoming dire. I pulled some more and finally exploded to the surface, and air.

Shaking water from my face and head, I took a huge, wheezing in-breath. I choked and spat water. I found somewhere I could get my feet down. Stood. Hit my helmeted head on the cave roof. I panted, hands on hips, waist-deep in turbid water, feeling sick.

I surged out onto a rocky beach and stood shakily looking back at the pool I’d just emerged from. I calmed my breathing.

I needed to pull myself together. There was no point hanging around. I strode on, further upstream, and soon came to the next sump.

I was on my own, in a place I had never been before, between two long flooded passages, dependent on my one light. I didn’t want to go on but now there was no choice. I was scared but once again I had to swim my way out under water with no hope of surfacing if anything went wrong.

Again there was a bolt securing a stout-looking rope that disappeared into muddy water. Sump 2 was supposedly easier than Sump 3, at 26ft long. The best route home was to dive this one and finally the much shorter Sump 1 which I had swum through several times before. John was waiting on the far side.

My heart was hammering. I knew I mustn’t hesitate. Anticipation always makes things worse. I checked my battery pack on my belt, that my light was secure on my helmet and boot laces tied. I was procrastinating. I tried to swallow down my fear. I took some breaths, then a really big one and dived in. This sump seemed narrow. I crashed into the roof, and the cave wall to my left.

I was so scared of letting go of the rope I ended up with a loop clutched in my two hands. Just pull, I told myself. I fended off the roof with my right elbow again. There was solid rock to my right. My helmet rattled. I pulled. The world was a muddy blur. I was progressing forwards. How far now? More pulling. Feeling short of air. Needing to breathe. Onwards, endlessly pulling on the rope, scrabbling with my boots. Then finally I was in air. I staggered out of the water again, shaky-legged. I didn’t pause to get my breath back. All that was in my mind was getting out of this cave.

I splashed onwards, jogging now, relieved I’d conquered the big challenges. Soon the pool that was Sump 1 was in sight. Someone had placed a stolen a street sign there. It read,

Wookey Hole 1½ miles

avoiding town centre

At that moment I didn’t care about cavers’ pranks, threw myself in and swam through. So easy. I surfaced and scanned around. Someone was crouched on a rock. When he saw me, he switched on his light and said, ‘All right?’

‘Yeah’, and I stumbled over and hugged him. I needed human contact.

He pulled out a squashed Mars Bar from somewhere.

I said, ‘John, you absolute star!’

‘Yeah,’ he said, ‘I know how to treat a lady!’

We shared the chocolate and headed back to the surface, peeled off wetsuits and made for the Hunters Lodge Inn. There I downed a pint or two of Somerset rough cider, regaled my caving mates with tales of my intrepidtude, and savoured some Type Two fun.

A photo taken not in Somerset but Nepal. This is from within Gupteswar Gupha, Pokhara