In the first of two episodes in the rich tropical waters of the Indian Ocean, the team explores its remote and pristine underwater worlds.
Expedition leader Paul Rose, environmentalist Philippe Cousteau Jr, maritime archaeologist Dr Lucy Blue, and marine biologist and oceanographer Tooni Mahto investigate how schools of manta ray suffering from shark bites are treated by the inhabitants of a remarkable reef. They go in search of one of the Indian Ocean's most elusive creatures, the dugong.
The expedition visits the only 'coral nursery' in this ocean, where an extraordinary technique is being used to repair damaged reefs.
They investigate what is driving the increasing trade in shark fishing, and working with the British Met Office, they take part in a global experiment to collect vital information about the Indian Ocean.