Iolo Williams sets off across the Great Barrier Reef in a bid to understand more about the place behind the headlines and whether it will survive for future generations. In recent years reports of mass coral bleaching have thrown a spotlight on reef. There are claims that more than half the reef could now be dead and the fate of the myriad of marine life the reef supports has become a worldwide concern. Iolo sets off to build his own picture of the state of the reef ecosystem, exploring the outer reaches of the reef and travelling inland to the rainforest in a bid to understand the human impact on the current health of the reef. Iolo discovers an abundance of wildlife on parts of the reef, but also sees some signs of coral death. Travelling inland to the rainforest he meets a farmer who has changed his practices in a bid to protect the Great Barrier Reef, and encounters an ancient inhabitant – the Cassowary bird, a creature that is vital to the health of forest and the reef beyond. An explorer at heart Iolo takes the opportunity to dive at night on the reef and fulfills his dream of seeing sharks hunting for prey before setting off on the next leg of his journey.