"You know, the rescuers could hear him hitting his air tank on the rocks as he tried to conjure up help from the darkness," says guide Trevor Roberts. A faint ring of metal on rock. Alone in the dark for days. They didn't get to him in time.

"A bad way to die," I think, squeezing through a 40m-high crawl space, fingers scrabbling in mud and rock slick with runoff from the surface, keeping my surging panic under control.

Miners do this every day, I think, imagining the appalling heat 4km underground, crouched in a stope, sliding around fragments of blasted rock, the thunder of a compressed-air drill making the ears ring for the next 20 years, a bit like for retired artillerymen. So it could be worse.

I have a recurring nightmare in which I get crushed by something massive and unknown while I lie in bed. I know, in daylight, that it's only pins and needles from lying on my back, but down here in this hole, this twisted craziness of dark tunnels and tight dead ends, dripping water and mud, the feeling is there.

It's wet down in the cave. The water works its way through the rock over months. The water you see dripping here has taken about six months to work its way from the surface. Stop for a minute and all you hear is the drip and trickle of water into pools you cannot see.

It's no secret that caving is highly dangerous for the inexperienced. Exploring some systems requires the combined skills of rock climber and miner. Some caves are full of water, and there are people - and they are crazy - who get their kicks drifting down cold tunnels, drifting because a careless kick of a flipper will stir up centuries of sediment and cause an underwater dust storm.

Underground, all bets are off when the lights go out. Lose your light and you're toast. To try, I wait for the others to move ahead then turn off my headlamp.

It is difficult to prepare for this kind of darkness. You hope that you will pick something out and hold your hand up in front of your face. And here's the kicker: you know you're holding up three fingers but a little voice whispers: "Are you? I can't see them . . ."

Edited from this article