Africa's Piranha: The plains of Africa have always been a hotbed of predator action, but lurking in its rivers is perhaps its most elusive killer: the Goliath tigerfish. Legends say they are man-eaters, that even crocodiles fear them. Locals call them "demon fish" but angling legend Andy Coetzee calls them something else: an obsession. He dives into the predator-infested Okavango Delta and the treacherous Congo River on a mission to finally land what is considered to be the hardest fish in the world to catch.