There were six of us in the minibus on the way to the Waitomo Caves, all looking ridiculous in wetsuits, ankle-length wellingtons and miners’ helmets, each clutching an inflated inner tube out of a tractor tyre.

We squeezed through a gash in the side of the mountain and climbed down into a chamber, stooping and huddling together to fit. I was nearest to the crevice which led further in, so the guide sent me on ahead and told me to stop when I heard a roaring sound. I inched along between the walls, splashing through water, seeing what little the lamp on my helmet cared to light up, and listened for a roaring sound. I realised what it was when I heard it.

All I had to do, the guide said when the others caught up, was to approach the waterfall backwards, stand on the edge, hold the inner tube up to my bum as if suffering with haemorrhoids and leap backwards into the water.

The sensible part of my brain warned me sternly against it, as if I were five and it were my father grabbing hold of my arm to stop me running into the road. Fair enough, as I never got round to learning to swim. But if I listened to the sensible part of my brain, I would still be at my desk in London, alternately stressed and bored. I would be on the Tube, instead of on a tube.

I backed up to the edge and jumped, ducked under and swallowed a mouthful of nasty water, then bobbed back up on my tube with the endorphin rush you always get when your brain says no and you go ahead anyway and come out of it okay.

We reclined on our tubes and floated along the underground river which led through a passage with stalactites bearing down on us, until we got to another waterfall, twice the height of the first. I stood back and let the others go first – “no, no, after you,” I said with the pantomime politeness of the British, and nothing to do with being scared – then jumped and sank deeper and ingested more water and came up choking and spitting, but felt fantastic as soon as I could breathe again.

We switched off our lamps as we came out in a cavern and stared up at a roof which was speckled with glow worms and looked like a diorama of space. There were thousands, no tens of thousands, an uncountable number of blue-white dots of effulgence stretching as far as I could see.

We slid silently through the darkness and the LED’s on the backs of the helmets advanced in a line and wound round the corners and the glow worms winked above us until the river burst out above ground through a fissure in the rock and we came out squinting into the afternoon sunlight.

© Richard Senior 2015

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