Greg James joins Dara Ó Briain, Jack Dee, Mel C, Chelsee Healey and Phillips Idowu for Hell and High Water: a five-day, 110km whitewater canoeing expedition down the Zambezi River in Zambia for Comic Relief. Crocodiles, hippos, mosquitoes and treacherous rapids await as six celebrities brave the elements to raise money for girls' education.