Uncomfortably numb: Personal watercrafts, otherwise known as jet-skis, enjoy a close working relationship with dock walls. Emma Cook steers into trouble

Mervyn Phillips, manager of Docklands Water Sports Centre bought his first jet-ski 12 years ago. Within six weeks he had sold up his garage business and emigrated to the South of France to devote himselt full- time to his new-found addiction. 'All my life I was looking for something that would totally engross me,' he explains. 'This was it. A feeling of ultimate freedom.' He moved into the Docklands 10 years ago where he and his wife now manage one of the largest clubs in Britain.

The sport, referred to generically as personal watercrafts (Jet Ski being a Kawasaki product name), was imported from America about 15 years ago. As the sport's popularity has increased, so manufacturers have competed to develop more powerful engines. Top-of-the-range watercrafts can reach over 60mph. With such high speeds there are some risks. Phillips lost his leg in a competition seven years ago. 'With racing you either go for it or you don't . . . You have to expect the occasional mishap.'

An hour later, feeling less philosophic than Phillips, I complete a liability form before trying out the sport for myself. It's a Sunday afternoon and King George V Dock is already full of jet-skiers churning up the water. 'There's no danger,' says John, my teacher for the afternoon. 'As long as you can swim and steer clear of the dock walls.'

The jet-ski, a mini-motorboat with handlebars, sucks in and blows out water to propel the rider forwards. In the pouring rain I immerse myself from the waist downwards in the black and icy waters of east London's dock. From the jetty, John takes me through the basics. 'Start her up and slowly turn the throttle with your right hand. Accelerate and then bring your legs up so you can kneel on the back.' The final stage, he tells me, is to lift both feet onto the ski and stand up. 'Do try to avoid other racers.'

By the end of his short lecture my lower body has turned numb. Concentrating on the controls, it doesn't take long to discover that the throttle is highly responsive. The slightest touch catapults the machine loudly and uncontrollably across the water. Yet as soon as the right hand relaxes for a second, it stops dead. This sport demands expert throttle control - without it standing up is an impossibility.

Barely able to keep hold of the handlebars, I give the throttle one last blast as we approach dry land. The jet-ski seems less sensitive to stopping than starting and the nose collides loudly with the dock wall. 'For God's sake don't accelerate when approaching walls,' John yells. On close inspection the jet-ski is unscathed. Embarrassed and twice my weight in a wet suit full of water, I am hauled out of the dock.

Judging by the reaction to my near miss, it's not the cheapest of hobbies. A brand new jet-ski costs between pounds 3,000 and pounds 6,000, or pick up a second-hand one for pounds 800. Yet watercraft ownership has risen to over 7,000 in the last year. The sport also appeals to both sexes. 'It doesn't rely on just strength,' says Phillips, who teaches a women-only class. 'What counts is agility and co- ordination - skills that come naturally to females.' Although Phillips is more involved in teaching since losing his leg, he is still a keen participant. Two years ago he jet-skied 438 miles around France, setting the European distance record. 'I'll never give it up,' he says. 'When I'm out there with miles of water to churn up I feel like the freest person on the planet.'

Docklands Water Sports Centre, pounds 20 per half hour (071-511 7000). Personal Watercraft Association (0703 616888)

(Photograph omitted)