Imagine a ferocious marine hunter up to 20 metres long, weighing twice as much as a humpback whale and ten times more than Tyrannosaurus rex. With jaws that open three metres wide, crammed with 276 serrated fangs, it can bite down with the greatest force of any animal that has ever lived.This is the Megalodon, and it once existed three million years ago. Next to the dinosaurs, wiped out 66 million years ago, it is but a stone's throw into our murky past when monsters reigned. Its name means 'giant tooth' but everything about it is gigantic: its exceptional lifespan, each stalking the ocean deep for more than a century, and its pups, born at more than two metres long, having likely eaten their siblings in the womb. Marking a milestone in paleontology, acclaimed conservationist, palaeontologist and explorer Tim Flannery and his scientist daughter Emma tell the story of this enthralling great shark.