Waterworlds

Secrets of Our Living Planet showcases the incredible ecosystems that make life on Earth possible. Using beautifully shot scenes in the wild, Chris Packham reveals the hidden wonder of the creatures that we share the planet with, and the intricate, clever and bizarre connections between the species, without which life just could not survive.

Discover previously unknown relationships, like why a tiger needs a crab, or why a gecko needs a giraffe. Each week Chris visits one of our planet's most vital and spectacular habitats and dissects it to reveal the secrets of how our living planet works.

In this episode, Chris travels across the world, from Iceland to Brazil, to Bangladesh and the Maldives. His aim: to reveal the secrets of our watery habitats, fresh and salty.

The extra ingredients, carried in water and necessary for life, are oxygen and sediment. But it's how the animals manage these resources that determines whether a habitat can actually support much live.

In the Brazilian Pantanal, Chris witnesses a riot of life, in a land where everything seems to be a giant: the snakes, the big cats, the otters, the fish - even the lilies! The reason? Well, it comes down to a very unassuming mollusc, the apple snail.

In the Sunderbans swamp of Bangladesh, Chris shows us how crabs create an environment fit for mangroves, deer and tigers. In the Maldives, he meets the hero of the coral reef - the sponge. And in the deep ocean, Chris meets the biggest (or smallest) hero of them all. Plankton not only feed our ocean giants, they even influence our atmosphere and climate.