Researchers from the BBC explore the waters of the Yangtze River in search of a single specimen of the Baiji River Dolphin. Although some fishermen and residents in the area claimed the presence of some individuals, the fact is that the expedition only proved that they are definitely extinct, mainly by the lack of solutions to keep them alive until it was too late. This river, remains polluted by industrial and agricultural waste so other species that live there are also at risk.