Swakopmund, Namibia. A mind-bending, hallucinatory place: an authentic slice of small-town Germany deep in Southern Africa. Cutesy, pastel-coloured Jugendstil buildings. Signs on store fronts in Gothic script, all umlauts and harsh consonants. A Lutherian church; a bierhaus selling good lager and sturdy plates of sausage and sauerkraut.

Leave town early in the morning in an old Volkswagen minibus. The sandboards strapped to the roof; a mangy dog standing on my knees so it can look out the window, wobbling as it tries to keep its balance.

Arrive at the dunes. Take down a sandboard, change into snowboard boots; trudge up the long curving track to the top. Grab a cloth, dip it in wax and smear it over the bottom of the sandboard. Find a place to sit at the edge of the slope.

Third in line. The first guy struggles to stay on his feet, falls over a few times, wobbles, squats and touches the ground, as if reassuring himself it is there. The second is an experienced snowboarder and streaks down the dune at speed, slaloming round imaginary poles to show off.

My go then. Follow the instructions: turn my back to the slope, do a backwards roll. Straight away scudding diagonally across the dune, balancing better than expected.

Picking up speed. Halfway down. Much faster now; faster than feels comfortable on a first attempt. Shift my weight to my toes to slow the board; but it digs in and stops dead and the kinetic energy flings me forward onto the sand and rolls me like a barrel with the board still clipped to my boots.

Unclip from the board, spit out the sand, empty it from each of my pockets in turn, wipe the thick off my arms, then plod back up to the top of the dune.

“You looked like a helicopter trying to take off sideways,” someone says.

I get further down the slope on my second run then come off again, but not as spectacularly. Land head-first. Glad of the pisspot helmet. But it rattles my brain nonetheless. On the third run – or it might have been the fourth – I glide all the way to the bottom and feel good. The snowboarder, by then, is doing jumps.

Move to a different slope, and a different, brutally straightforward, style of sandboarding. Take a big sheet of plywood, lay face-down on it, lift my feet, grab the corners and curl them up, then just hang on as the board careens down the slope. There is no slowing, or stopping, or steering, as there is with a proper sandboard: just staying on or coming off. It feels stupidly fast – I will find out how fast – and totally out of control, which I suppose it is, except I could bail if an unexpected springbok suddenly heaves into view.

Whisk past the guy at the bottom with the speed camera, heading for the run-off slope. Somehow hit it at the wrong angle, bury the board in the sand, fly a few metres then bury myself. Spit out the sand, shake it from my hair, rub it from my t-shirt, empty my pockets again.

“65k,” the guy with the camera says.

© Richard Senior 2016