Overview:Chris Packham explores what lies beneath a crocodile's hard exterior, to discover the secret to its 250-million-year history. It may look like a relic from a prehistoric world, but the crocodile boasts one of the most sophisticated physiologies on the planet. By following all stages of a crocodile hunt from the warm-up to the ambush and the kill, Chris reveals how their extraordinary circulatory system enables them to hold their breath under water for over an hour, how exceptionally sensitive skin detects their prey, through water, from over 20m away and how anti-bacterial blood means they can feast on anthrax-ridden meat.