Barb’s lips are turning a frosty shade of blue. “This,” she says, grimacing and shivering, “is bat-shit crazy.”

Given that we are wearing wet suits, helmets, running shoes, and buoyancy vests and are about to wade off a perfectly good Welsh beach into the roiling Irish Sea, I am quite convinced that she is showing great restraint in her description of our current situation.

Matt Shaw—mountaineer, first-aid attendant, and coasteering crazy man—stands before us. He works as a guide for Surf-Lines, a multisport adventure company in northern Wales. To suggest that Matt is keen on the art of oceangoing lunacy called coasteering is akin to suggesting a seal might enjoy leaping for a fresh fish.

“ ’Kay, guys,” he says as we stand at the edge of the windswept shore, “let’s all jump in now, right?”

With that, he bounds into the heaving September sea as if a) it’s not cold as shit outside, b) the surf is not pulverizing the black rocks, and c) his actions are within the parameters of normal behaviour.

As my already wind-numbed feet hit the water, I gasp. I try to catch Barb’s eye. It appears to be squinched shut. She seems to be muttering. I’m not hearing her too well over the waves and my own glorious new combinations of expletives.

My fingers curl into frozen claws. If I could feel or see my feet, I’m quite sure they’d be a thrilling combination of mottled purple and white.

“ ’Kay, guys,” Mr. Enthusiastic says. “We need to practise swimming with our feet in front of us, so that we can get up on the rocks without bashing ourselves.”

Silly me. I had thought smashing around in the waves would be good enough to tick this coasteering thing off the agenda. I was wrong. Why, oh why, had I signed up for this? And then…Matt cheerfully informs our group of eight that we will be spending the next two hypothermic hours doing this mad sport. He says this as if it’s a good thing.

Indeed. We will be scrambling up jagged cliffs, jumping off those same rock faces into the surging sea, and swimming against waves that could easily drown several large horses and a stagecoach.

It’s said that this ridiculous sport came about because Welsh mountaineers ran out of mountains. In spite of the diminutive size of Wales, there are some wonderful ranges (and mountains like Snowdon, where Sir Edmund Hillary practised his techniques before his epic climb of Everest). But apparently, there are only so many times one can climb the same mountain. The mountaineers started to look at their rocky coastlines to expand their repertoire.

Then, because they’re Welsh and they’re mountaineers, they began purposefully throwing themselves off the rock faces. “Hey,” I’m sure they said as they spit out another smashed-asunder salty tooth, “let’s call this coasteering!”

“Timing is key, guys!” Matt’s words fly toward us on a gust of wind. So it would seem. The idea about having one’s feet out in front is great except for one minor detail: the swells shove me toward the rocks and just as suddenly suck me away with a vehemence that feels malevolent. Suddenly, that tired old phrase “So near and yet so far” is fraught with new relevance.

Finally, I’m flung onto the side of a rock. I cling to the stony wall, stuck like a half-dead limpet. I’m too scared to find my next toehold. The sea bashes away, determined to kill me. Matt appears. “Right. You’re doing great, here’s a great spot.” He points to a minuscule rocky outcropping. “Just keep going!”

Somehow he magically appears for everyone at once, inspiring confidence while pushing, cajoling, and infusing us with his exuberance. He is coach, teacher, leader, and inspiration wrapped up in one incredibly fit über-enthusiastic man.

Surprisingly, my hands warm up as we bob in the swells, probably because my heart is thumping harder and faster after every jump off the rocks. Meanwhile, a grin is threatening to split my numb face.

We all perch on an outcropping while Matt bobs in the surf below. Between swells, he shouts, “Go one at a time—swim past me to that next cliff and then climb up. When you get to the top, I want you to jump!”

He smiles and points to the cliff across from us. Apparently, we are about to pretend we’re Acapulco cliff divers. I wait my turn, and then, in spite of myself, swim across the surf and crawl up the cliff. I stand, wavering, at the top. The others wave and yell encouragement. Finally, I decide to quit thinking and jump.

Two hours—time that I’d been sure would stretch interminably—is over too quickly.

“This is the last bit, guys. Stay focused.” We scramble our way to the top of the highest cliff yet. I flop into the purple heather and yellow grass and hang my head over the edge to watch the frothing waters rush the rocks below. My salty hair is plastered across my head.

I can’t remember the last time I felt so alive and connected to the elements. Or, as Matt would say, “Atmospheric, guys!”

If you ever get a chance to go to Wales, take it. Practise the art of the coasteering fling. It’s guaranteed bat-shit-crazy fun.

Access: The writer travelled as a guest of VisitBritain. For info on coasteering, see the Surf-lines website.