Now this is what I call a change of perspective. In my former natural habitat, I resided at sea level, eyes fixed on the horizon or on weather charts, searching out waves and coming to life with each new swell. However, I got bored with waiting for the waves and the adventure to come to me so there had to be a sea change.

Blinking in the sunlight, fingers feeling across the rough surface for a firm hold, toes balanced on a narrow ledge, I feel like an urban myth retold. You know the one about the scuba diver found in the middle of the forest? Well here I am, a displaced surfer half way up a 70ft rock face as if deposited by some freak wave.

Roche Rock is an awesome spot. This granite and tourmaline crag rises from a rough Cornish heathland to be capped by the eerie ruins of an abandoned hermitage chapel sprouting organically from its summit. From 35ft up I have seen my next move, which is fairly exposed and feels like a leap of faith. I am now closely examining the daubs of lichen in front of my nose that cling to the rock with a determination only matched by my fingers.

"Don't forget to breathe," shouts my guide from below. "Holding your breath only increases feelings of anxiety." How on earth can he tell from all the way down there?

Fuelled by a heady cocktail of fear and adrenalin I trick my mind and body into pushing off from the safety of my ledge and swinging out into the unknown. It's not often I turn to film directors for guidance, but Baz Luhrmann once said, "Do one thing every day that scares you." I don't think that is bad advice, and researching this book – whether climbing, surfing mountain biking or kayaking – has let me follow that philosophy. In the same breath he also said, "wear sunscreen". With the sun's rays reflecting off the rock, freckles already filling my face to capacity, I really wish I'd followed that piece of advice better.

Footprint's 'Green Adventures Britain' is out in June (£19.99)