I have two oxygen tanks strapped to my back and I'm halfway up a mountain in Switzerland. My dive buddy and I waddle in our flippers to the lake's edge. The temperature is several degrees below freezing but the pistes are packed; the snow is deep and the skiing is good. We check our mouthpieces and brush the snow off our facemasks.
My buddy taps me on the shoulder. It's the signal to sit on the pool's edge. Above us, skiers look down from an Alpine gondola. Another man gives us a thumbs-up - the signal to make our dive. The dark depths of the glacial lake in the shadow of the Matterhorn await us.
Ice diving is the latest winter sport, endorphin-surge fad and adrenaline fix. The Zermatt Ice Rock Club is the world's first, and as yet only, ice-diving school and is run by French former marketing executive Gerard Garson, who gives me my dive signal.
For 400 Swiss francs (HK$2,500), all equipment and limitless oxygen included, you can learn to dive under the snow 3,440 metres above sea level in mid-winter in the middle of Europe. A two-day course consists of three 20-minute dives in a frozen-over glacial lake. The school is open from December until the end of April.
'It is the only sport where two pounds of high explosive are required before you can even start,' says Garson. 'Every time we dive we must first get permission from the local authorities, then clear a hole in the ice using a small charge of dynamite. Safety is paramount before, during and after the dive.
'Preparing for the dive is the most exhausting thing. Shovelling and brushing away all the exploded snow cover so we have a safe snow hole isn't easy, especially at altitude,' he says. 'We get some funny looks from passing skiers. Sometimes we go into bars in town wearing our scuba outfits.'