Day one of Comic Relief's Hell and High Water challenge sees Greg James, Dara O Briain, Mel C, Chelsee Healey and Phillips Idowu tackle the mighty Zambezi River in traditional dugout canoes. Battling ants, intense heat, circular boats and their own inexperience, the team makes slow progress downriver—and things get tougher when they ditch their local guides and try to navigate solo, leading to panic and a swift return to professional help. Tonight: camping on an island with hippos, crocodiles and mosquitoes.