Jackie Hunt isn’t known for treating her passengers gently – just ask one of her previous navigators. “I spun the boat on a corner and chucked the poor guy out. All that was left on the deck was a pair of shoes,” she says. “But don’t worry, you’ll be fine. If you get scared just nudge me and I’ll stop.”

I nod my head inside my crash helmet and grip the steel bar in front, as instructed. I have been charged with navigating on what will be Hunt’s last training session before she flies to Malta to compete in the first race of the 2007 P1 Powerboat world championships this weekend.

Although she says she will be taking it easy, and although the boat we are in today is her slightly smaller training vessel with only 400bhp rather than her P1 racer at more than 1000bhp, there is something in the way she floors the throttle that says Hunt doesn’t do things by half.

The noise from the two outboard motors changes from a gurgle to a roar, the tip of the bow rises above the horizon and I am thrown into the back of my seat with a force that snaps the helmet visor shut. In front of me the digital speedometer clicks up past 50mph, 60mph, 70mph. The boat is skimming across the flat waters of the Solent off Southampton past yachts and dinghies, speedboats and cargo ships. It feels as if we are floating on air.

Hunt is having a blast and so am I. Then she turns to me and points to a large passenger ferry on our starboard side, travelling in the opposite direction. She shouts for me to wave. I grin uncomprehendingly and start to release my grip from the bar, realising too late that this is not what she meant.

Passengers on that ferry last Sunday at around 1pm would have seen a 30ft powerboat called Zing a Ling shin up their wake then continue its upward trajectory clean out of the water, gliding through the air momentarily before splashing back down in a shower of spray just in time to meet the next wave and take off again. It would have looked like a laugh.

But on board it was not funny. Each landing shook me from my seat, the extra weight of the crash helmet forced my head backwards and forwards with additional force, and with each concrete-hard impact the fear grew of being jettisoned – trainers and all. I wanted to nudge Hunt but my hands were frozen to the steel bar, and besides, she was laughing her head off.

Jackie Hunt, 37, doesn’t look like a maniac. Then again, she doesn’t look like a world champion either. But she is both. Small and blonde, she needs to put cushions on the seat of her boat so she can see over the steering wheel, despite which last year she won the P1 Powerboat world championship with co-pilot and husband Mike Shelton. She is the only female ever to do so, and the only female driver in the series.

P1 bills itself as the most spectacular sport of its kind, with boats regularly reaching 90mph and negotiating sea swells of up to 13ft. Unlike the better known Class 1 Powerboat championship, P1 is open to everyone and provides more spectator excitement because the races are set close to the shore. In motoring terms, think of it as the equivalent of touring car championships: a real world alternative to the rarefied glamour of Class 1 – the Formula One of powerboating.

“Class 1 gets all the coverage, but really you have to be a millionaire to get involved,” says Martin Allerton of Powerboat P1. “It is for rich boys with their big toys. P1 is much more accessible and is aimed at people who love powerboating but can’t afford the huge costs of Class 1. There are so many talented drivers and sailors in Britain, and this series gives them the chance to race.”

The season comprises six grand prix races throughout Europe, including the British Grand Prix at Cowes in August, and two classes of boat: SuperSport, which Hunt competes in, and the more powerful Evolution class. Each grand prix consists of a rally of 50 nautical miles and an endurance race of 80 nautical miles.

The SuperSport boats have a top speed of around 90mph and are essentially standard production boats, but without cabins or kitchens. They have two inboard motors of around 500bhp, which provide a power-to-weight ratio of 1bhp per 4.5kg. For comparison, the super-light Lamborghini Gallardo Superleggera boasts a ratio of 1bhp per 2.5kg, but the car isn’t 39ft long.

The organisers claim this is one of the fastest-growing sports of its type; last year’s British Grand Prix attracted a crowd of 65,000. And this year the SuperSport class will see 20 boats, including teams from China, Italy, Belgium and America.

Hunt’s rise to the top hasn’t been easy. She claims to have encountered hostility from male competitors, but says she likes to let her driving do the talking. “The aggressive male attitude can sometimes be a hindrance. Women drive differently – slightly calmer – and don’t get carried away. Mind you, I couldn’t do it without Mike. We have a great understanding and we egg each other on. When we’re in a retirement home we’ll be racing our wheelchairs.”

Despite its billing as a cheap way to race, P1 is hardly for the impecunious. Hunt’s boat – the Extremeboat.com – cost around £200,000 and the season’s running costs total about £70,000. To finance it she has a market research job, where being world champion doesn’t cut much ice with clients. “It keeps me down to earth but I’d rather be racing,” she says.

The sport isn’t for the fainthearted. Between the 1970s and 1990s there were several high-profile deaths in powerboating, not least that of Stefano Casiraghi, husband of Princess Caroline of Monaco. Although today’s safety regulations are more stringent, travelling at nearly 100mph on water is never predictable. “There is a risk that you can bounce off a wave during the race and land on another boat,” says Hunt as we pootle back to the moorings. “But the worst thing you can do is ‘stuff it’. That’s when you go through a wave rather than over it, and all of sudden you become a 100mph submarine, the force of the water around your neck choking you and trying to pull you off the boat.

“That’s the thing with boats: unlike with cars, your ‘road’ is constantly changing.”

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