Extracts from the book

"With my eyes closed but my focus bright, I pinched shut my nose and exhaled against it. Concentrating on equalising the pressure in my ears, I let the rest of my body relax as I passed through the thermocline, a layer underwater separating the warmer water above from the cooler water below. Equalise, equalise, equalise. I was still descending, the water rushing over my body. Eventually I felt there was no air left to equalise with and I let the weight go, opened my eyes and caught hold of the line.

"I looked down - first a couple of metres to where the weight had stopped, and then twenty metres further to the ocean floor, undulating away forever on all sides. I saw a secret, silent landscape of rocks with grasses moving in a watery breeze. I looked out to see how far it went and saw to my delight a shoal of black fish in the distance suspended like tiny black stars against a blue sky. We all hung there, so still and quiet."

"Look at your watch. How many breaths are you taking each minute? Is there any strain? You should be completely relaxed, with no strain on the out- or the in-breath. Delight in the sensation of peace. Breathe out deeply, then in more deeply and very slowly for a count of five and then hold your breath.

"Notice how your body is feeling. Do you feel euphoric? Strange? What passes through your mind?

"Allow shivers of anxiety to pass. Relax into your body, still your mind.

"To hold your breath is to suddenly become still: to become a silent observer and participant in the wondrous workings of our bodies. Feel the sensations as they come and go. Do not be alarmed by them. Feel the first stirrings of the urge to breathe.

"Your diaphragm may contract. Relax some more but do not strain. Ease into the hold.

"And then release, take at least three quick and deep breaths to recover, then breathe through your nose normally."

"As a child I dreamed of weightlessness. Frustrated with a clumsy body, I struggled in gym class to spring up and catch, just for a precious second, the feeling of air beneath my feet. Afterwards, lying on hot summer grass, I watched birds wheeling freely on the wing and yearned to feel that lightness. Behind the birds I could see the brushstrokes of aeroplanes, man’s machines that defy natural laws and take us where our bodies cannot.

"Weightlessness, the freedom to move in three dimensions, would always elude me until I learned to slip beneath the surface of the sea and explore a liquid space where fish flitted as freely as birds.

"In space there is no sound, no touch, no smell and no taste - only silent floating. On one breath, under the water, our senses of smell and taste are stilled and our hearing muted. We are left with our sight and the invisible caress of the water moving around our bodies. This narrowing of external stimuli opens the petals of our sixth sense, which flourishes in the void.

"Our sixth sense reveals deep connections and feelings that have no logic and cannot be described with words. It takes us from the tiniest particles within us to the vastness of the universe beyond. We are all separate and at the same time we are all one.

"Often on a freedive I would close my eyes. I wanted to be an astronaut, floating through the dimensions of infinite black space, surrounded by the tiny lights of a million stars. But in the water, sunlight was always playing on my eyelids. To spacewalk on this earth I would have to dive at night."