S1, E2: They may be the most isolated in the world, but every one of the region's 20,000 islands has been colonised. This is the story of the ultimate castaways - from saltwater crocodiles and giant eels to crested iguanas - who have reached islands thousands of miles apart. The voyages of the South Pacific's first people, the Polynesians, were no less remarkable. Their journeys were some of the greatest ever undertaken.