The remaining rookies get their first taste of underwater filming, moving to the island of Zanzibar, as the series in which a team of wildlife enthusiasts compete to win a job with the BBC's prestigious Natural History Unit continues. The contestants must use snorkelling and free-diving techniques. After the intensity of working in swamps, deserts and mountains, this at first seems like paradise but they soon discover that working underwater requires stamina, planning and a fair whack of nerve. they are challenged to film dolphins using snorkelling and free-diving techniques as well as state-of-the art recording equipment. Back at the camp, they have their work assessed by James Hoyborne, Nick Knowles and expert diver Tooni Mahto. They also learn who will make it to the next location and who will have to go underwater again to capture images of a whale shark.