Icy water crashes over the side of our life raft as it battles through the waves. Only the lightning illuminates the blackness around us. I'm soaked to the skin, freezing cold, and whey-faced with seasickness when a strong wave sends me careering across the raft and into Bear Grylls. There are worse people than the TV survival star and ex-SAS man to be all at sea with, I suppose.
Except, we are not at sea. Minutes later the lightning stops; the water calms down, and my stomach stops churning. This is not some elaborate fakery for Grylls's TV series Born Survivor – although the adventurer is reportedly no stranger to that – but a hi-tech training exercise to prepare him for his next adventure: attempting to become the first man to navigate the whole of the treacherous North-west Passage in a rib. (That's a Rigid Inflatable Boat to folks back home.)
Our little vessel is floating on a vast pool at the Royal National Lifeboat Institution (RNLI) sea survival centre in Poole, Dorset. With me is the four-strong crew that will accompany Grylls on the infamous 3,000-mile crossing, which includes an ex-Special Boat Service boat handler, a marine engineer and an ocean racer. As a sedentary journalist, it is fair to say I am out of my depth.
Moments later this is literally the case. While the thought of wrapping their legs around Grylls's waist may delight the adventurer's female fans, doing so while trying to swim in sync to offer mutual assistance proves faintly ridiculous, and no mean feat in waterlogged yellow oilskins and wellington boots.
Apparently, learning this, along with capsizing the right way, mastering the life raft and being picked up by a helicopter are all vital skills that could make the difference between life and death on the crew's forthcoming expedition.
I'm not alone in floundering in the swell. Tim Levy, chief executive of Future Capital Partners, the company funding the trip to promote the use of new fuels such as bioethanol, has also never sailed before. "I've got no experience, none at all," the 47-year-old says, his cheerful face poking out of a white helmet as he bobs up and down in the water. "It is just a crazy idea that I cooked up with Bear."
Feeling sicker by the minute as yet another wave crashes over my head, I'm inclined to agree with him.
"People freak out. They get sick, too. Even the most experienced people get sick," assures the RNLI representative Paul Cullen.
Grylls does not look remotely sick. The married father of three looks tanned and relaxed, having just returned from Los Angeles, where he was shooting his new TV show about surviving Worst Case Scenarios in urban areas.
Whether or not he will survive the North-west Passage is another matter, however. While the old Etonian's exploratory credentials are impressive – he became the youngest man to climb Everest at the age of 23 – the hazardous sea route takes no prisoners. When the Arctic explorer Sir John Franklin led an expedition in search of the shipping passage in 1845, his ships became locked in the ice halfway through the passage, forcing the 129-man crew to turn to cannibalism in their final days. No one survived.
This apparently doesn't deter Grylls, who insists: "I love being in remote, difficult places with good friends. It is where the best bonds are made. Fighting the cold, the long distances, navigating through ice, and also the uncertainty of finding out if the ice has actually broken up enough to allow us to sneak through, are where the risks come in."
Icebergs probably pose the biggest threat. In 2008, extreme cold weather stopped even an ice-breaker from getting through some sections of the passage. But Grylls is confident of support from a force stronger still. As an evangelical Christian, who tours prisons and schools talking about his faith, Grylls hopes that God will be watching over him. "I am yet to meet an atheist in the Arctic Ocean in a small boat," he admits.
Unusually for the camera-hungry Grylls, the trip is not for a TV show, but to highlight global warming while fundraising for the children's charity Global Angels.
If it is an attempt to repair Grylls's tarnished reputation, which took a battering when it emerged he bedded down in hotels while filming a so-called survival series that claimed he was stranded on desert islands and in the Sierra Nevada mountains, he is not letting on.
"I've got to a position of responsibility and want to drive home the message about global warming," he says, smiling, the Hollywood-white teeth a reminder that the country's Chief Scout is now a global TV star, his shows are watched by more than one billion people worldwide. "The Scouts are so motivated by this issue; it will be one of these 15-year-old kids grown up who will change things."
As if on cue, a line of children press their noses to the window outside, desperate to catch a glimpse of the adventurer.