A team of stars including Irish comic Dara O’Briain will brave crocodiles, hippos and huge rapids by tackling more than 100km (more than 60 miles) of the Zambezi River.
The group – which also includes actress Chelsee Healey, Radio 1’s Greg James, Jack Dee, ex-Spice Girl Mel C and triple jumper Phillips Idowu – will be pushed to the limit as they take on the back-breaking journey in dugout boats, canoes and white water rafts for Comic Relief.
They will be paddling for up to eight hours a day during the five-day ordeal as they negotiate the African river.
During the 111km (68-mile) journey, they will face rapids known as Gnashing Jaws of Death, The Washing Machine and Oblivion on their way to the world’s largest waterfall, Victoria Falls.
Their 'BT Red Nose Challenge: Hell And High Water' will see them shunning luxury accommodation en route and instead they will be camping on cliff-tops and watery riverbanks as they nurse their blisters and rest their aching limbs.
Armed guards will accompany them to protect them from wild animals as they recharge.
The journey, which it is hoped will raise £1m (€1.2m), is being staged ahead of this year’s Red Nose Day which takes place on March 15.
Mel C, who is a veteran of Comic Relief projects after releasing a single for the charity with the Spice Girls in 1997, said: “It’s going to be tough.
“It’s going to be physically and emotionally demanding, but we’ve all got each other and hopefully we’ll be able to get through it.”
The group has already been put through its paces with training at the Lee Valley White Water Centre, used as the canoeing venue for London 2012.
Dee said: “It was an important day of training to get us ready for being on the Zambezi. Whether it’s actually accurate I don’t know.
“I have a sense that it’s probably like having a go on the dodgems in order to go and do Formula One at Monaco. I suspect the difference is going to be fairly considerable.”
O’Briain said: “When I was first asked to do this challenge, I did a quick Google search of Zambezi rafting but after the 10th page of people being instantly flung into the water I turned off the computer.
“But lives can be changed if people put their hands in their pockets in exchange for our misery so that sounds like a fair deal.”
The proceeds will be used to help educate children in Zambia.
The stars can be sponsored at rednoseday.com/zambezi.
Red Nose Day celebrates its 25th anniversary this year, having raised more than £600m (€714.8m) for people in the UK and Africa.