What enters a man's head as he plunges 60 feet over a thunderous Icelandic waterfall in a tiny plastic boat? In Shaun Baker's case, it is likely to be his lunch. Followed by his heart, lungs and kidneys, as layer upon layer of suffocating protective clothing sends his internal organs in search of less restrictive accommodation.
The year is 1996 and the waterfall in question is the 64ft Aldeyjarfoss. Emerging from the bone-crushing cauldron of foam at the bottom, the 32-year-old Briton has just set a new world record for "freefall waterfall kayaking", one discipline of a little-known extreme sport which demands not only technical excellence, but balls the size of watermelons.
Fast forward five years to a freezing December morning. I've joined Shaun, now 37, at Hurley weir on the River Thames to take part in some "whitewater freestyle". A different kayaking discipline altogether from the extreme stuff, Shaun uses it to hone paddling skills. "Surfing" the static waves a river weir offers, freestylers perform turns and rolls, scoring points for style and technical merit. But he has good reason to stay sharp. Next spring, Shaun plans a "mainline" descent of Iceland's Godafoss waterfall; though a mere 40 feet, he will running the most dangerous route. He also intends to break his own "speed altitude descent" record, which currently stands at 19.9 seconds for negotiating 75 vertical feet of river. Added to these will be a first descent of the Iguazu Falls in South America.
By late morning a flotilla of junior paddlers are riding the four-foot waves. Then Shaun appears. Perched on a jetty, kayak awash with sponsors' livery, he draws admiring glances from his audience. Checking the surging water, he drops into the most torrid wave, taking his boat through spins and tumbles, displaying the form that has landed him nine UK freestyle titles and victory in the sport's first major international competition. The young boaters know they are in the presence of greatness. Remarkably, Shaun's skills are entirely self-taught. His parents bought him his first kayak in 1974, to channel his "obsession with water" – aged just 16, he paddled 700 miles from Kingussie in Scotland to Hell's Mouth in Wales, across some of the UK's roughest waters. It was only when he wanted to teach that Shaun undertook accredited British Canoe Union instruction.
"People ask when I got into extreme kayaking, but there was never a day when I thought, 'That's what I want to do'," Shaun explains. He makes light of his role as the sport's founding father; before Shaun Baker hauled his boat to the top of the world's more intimidating waterfalls, extreme kayaking was just. . . well, kayaking.
Pushing the boundaries of any sport always induces apoplectic jowl-wobbling among the establishment. Kayaking is no exception. "When I began to shoot waterfalls, older paddlers said I wasn't kayaking, I was simply throwing myself off cliffs," he says. "But I had worked out that I could control both my direction and landings. Now I'm shooting falls high enough for them to see my theories in action."
In stretching the sport's limits, Shaun's other achievements include "snowboating" in the Canadian Rockies – where this year he set the "kayak land speed record" of just under 40mph – and "sandboating" in the Moroccan desert. Indeed, he has brought the discipline so far that, in an overcrowded sponsorship market, he is now a member of the team of international extreme athletes that endorse the Red Bull drinks brand.
To the uninitiated, freefall kayaking looks like a victory for courage over common sense but Shaun's experiences reveal method in the apparent madness. Large rivers dropping from a cliff top offer paddle blades a dense "slab" of water to gain purchase, allowing Shaun to change direction ... until the water becomes spray, that is.
"The boat [tiny, and designed for use in swimming pools] should hit the water at angle of between zero and 90 degrees, depending on the drop – I alter that by shifting my body weight backwards and forwards," explains Baker. "The higher you go, the more perpendicular the boat must be in relation to the water's surface. When I land, I throw my upper body on to the back deck of the boat, to prevent compression of the spine. On a low fall this means I am pretty much lying down, but on the highest falls, I hit the water in a standing position."
Hitting the bottom perpendicular to the water's surface is all very well but, warns Shaun, "you need to get away from the bottom of the fall as fast as you can. The biggest risk is going so far under, you'll never resurface."
With safety a priority, Shaun founded his own company, Playboater, to research and develop extreme kayaking equipment. In addition to the two thick wetsuits he wears for each descent, Shaun squeezes into a constricting neoprene lumbar support, specially-made body armour, life-jacket and full-face motorcycle helmet. Such is the effect on his circulation, he must keep a careful eye on bloodflow to his hands. Yet despite the odd spinal compression and broken rib, Shaun's career has been relatively injury free.
When accidents do happen, however, they are serious. In 1997, Shaun was descending Iceland's Thyfafoss waterfall, "The Waterfall of Thieves". Taking a dangerous line for the benefit of a camera crew, he hit the bottom and was held underwater, "like a ping-pong ball under a tap".
"After about 20 seconds of fighting to resurface, I realised I was about to pass out and had no choice but to jettison the boat. I was giving away 200 litres of buoyancy and shot down like a rocket.
"When I began to see daylight, I took a breath, but all I took in was water because what I thought was the surface was actually spray. From the top until the time I was spat out was a whole minute. The recirculation of the water was huge and the safety crew were convinced I was dead."
And so Shaun contemplates the challenges the future will bring: "I have this vision of myself jumping off waterfalls when I'm a rickety old man. And all these kids will be watching saying 'Why does he do that?'
"The exhilaration of doing what I do is like nothing else on earth."
The British Canoe Union offer canoe and kayak instruction at clubs around the country: 0115 982 1100, www.bcu.org.uk.
For information on upcoming whitewater freestyle events visit www.hurleyweir.com. Find news and pictures of events in the world of extreme kayaking at www.freestylekayaker.com.
www.paddling.com offers reviews, manufacturer details, video clips, tips on tricks, retail, where to go, kayaking clubs.
Do and don't
Do learn how to 'eskimo roll', or right your canoe. If you don't you'll end up swimming – not fun under millions of gallons of water.
Do hire a 'safety boater' – nobody else will be stupid enough to help you.
Don't try this at home – extreme kayaking is about as dangerous as watersports get. Before you get involved, seek advice from the BCU (see 'the facts').
Don't be shocked by insurance premiums – if you think skiing insurance is pricey, extreme kayaking cover works out at about £9,000 per trip.
Mainlining Taking the hardest route down the waterfall
Sneaking a fall Claiming the first descent by taking an easy line
Syphon Potentially fatal channel of water hidden below the surface