Spice Girl Mel C put her oar in during a charity challenge on the Zambezi River when she whacked DJ Greg James in the head with a paddle as they tackled the rapids.
Radio 1 star James managed to continue and the group, which includes comic Dara O'Briain and actress Chelsee Healey, got off to a good start on their five-day ordeal negotiating the African river.
The group - which also includes Jack Dee and triple jumper Phillips Idowu - will brave crocodiles and hippos along a stretch of the Zambezi River and will be paddling for up to eight hours a day during the BT Red Nose Challenge: Hell and High Water.
O'Briain said: "We've done 22 kilometres and I can definitely say the second part of that has been just as painful as the first.
"Chelsee and I have been working as a team and in any usual circumstances our worlds wouldn't collide, but we've become like an old married couple today, bickering about rowing.
"The hardest thing so far is keeping the boat in a straight line. We've spent a surprising amount of today facing the wrong country and nearly ended up in Botswana a couple of times. But we're all aware it's likely to get worse and worse. This is only day one."
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.
The challenge 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 £1 million, is being staged ahead of this year's Red Nose Day which takes place on March 15.
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 £600 million for people in the UK and Africa.