Marine invertebrates are some of the most bizarre and beautiful animals on the planet, and thrive in the toughest parts of the oceans. Divers swim into a shoal of predatory Humboldt squid as they emerge from the ocean depths to hunt in packs. When cuttlefish gather to mate, their bodies flash in stroboscopic colours. Time-lapse photography reveals thousands of starfish gathering under the Arctic ice to devour a seal carcass. A giant octopus commits suicide for her young. A camera follows her into a cave which she walls up, then she protects her eggs until she starves. The greatest living structures on earth, coral reefs, are created by tiny animals in some of the world's most inhospitable waters.
Formed from the remains of a 2.5 million-year-old imploded volcano, the Ngorongoro crater is a study in contradictions: On one hand, it's a self-sustained and plentiful land that provides for the many animals that call it home. Conversely, its isolation threatens the existence of many of its key species. What does the future hold for this unique habitat?
At the start of his journey, Attenborough meets some of the people and animals that have made their home along the river in Zambia. He is invited to witness the Kuomboka festival, featuring the Litunga, chief of the Lozi people of western Zambia, and his people. In the festival they migrate from Lealui to Limalunga, before Lealui is flooded by the Zambezi. The spectacular ceremony consists of a fleet of barges, many containing the Lotunga’s possessions, making the journey up the river accompanied by heavy drumming of the royal Maoma drums. Other highlights include David Attenborough joining the Litunga as he opens the court and presides over the inauguration ceremony.