This documentary accompanies the shark explorer Richard Fitzpatrick to the Australian Great-Barrier-Reef, the largest marine sea park in the world and home of the tiger sharks. Fishing is strictly forbidden, yet also a mono-culture on land can threaten a whole eco-system. A river polluted by fertilizers used in the sugar cane plantations is killing the young fish of the sharks living in the mangrove swamps and the river mouths. Richard Fitzpatrick tries to stop the extinction of the sharks. He spends more than 100 days per year at sea, in order to explore the wandering, hunting and mating behaviour of the tropical shark species. He hopes to gain specific knowledge about sharks which could once ensure their existence.