We uncover nature's fiercest rivalries where oceans collide with land. From white sharks ambushing seals to polar bears battling walruses, this episode captures the ultimate frontier.

Cats are some of the most successful hunters on Earth. They share the same blueprint, but the unique challenges of their habitats shape their individual hunting strategies.

As the ocean's hunters prowl the seas, each masters its own way of survival. Their strategies differ, but the same rules apply: Assess, adapt, act.

The team take a paddle boat out for a rescue, a hunt for a sneaky gator ends in chest-deep water, and a gator with an eye problem gets a check-up.

Alaskans must take advantage of the long days to prepare for the long freeze that lies ahead. In Kiwalik, the Hailstones embark on a seasonal native harvest, hunting for seagull eggs along the river.

Alaskans must ensure they are prepared to withstand the extreme cold that lies ahead when winter arrives.

As the thaw draws to a close, Alaskans battle the clock to maximize their final days of sunlight in the Arctic.

The latest custodians of Chavenage House in the Cotswolds bring modern ambition to a newly inherited home. At Ashby Manor House, plans are afoot to revive a Tudor room tied to the Gunpowder Plot.

After 25 years of neglect, Pitchford Hall has returned to its original family, who now face a huge restoration task. Plans progress at Ashby Manor to revive the Gunpowder Plot Room.

The Great Barrier Reef, a series of coral reefs along Queensland's coast, is the largest structure created by organisms. It changes with the tides, the seasons and shaping forces such as erosion.

Only 7% of the Great Barrier Reef is made of coral reef. The rest is a variety of habitats including the world's oldest jungle, hundreds of islands, swamps, sand flats and meadows of sea grass.

However fascinating the reefs themselves may be, far more species depend on the environment they create outside. This occurs in Australia and its Indian Ocean waters in abundant number and variety.

We take in New Zealand's natural beauty from Fiordland - the home of the Hobbits - to Cape Reinga, the northern tip where wild horses run along lonely sandy beaches.

We meet the countess who runs Mapperton House. An old drainage tunnel threatens to become an expensive headache at Pitchford Hall, and Brancepeth Castle opens its doors for the annual Dragon Quest.

Chavenage in the Cotswolds tackles a new pond. The restoration of the Gunpowder Plot room at Ashby Manor becomes increasingly complex. And the Victorian Treberfydd House has never been bought or sold.

The Spinosaurus is one of the strangest dinosaurs to have ever lived; a discovery in Spain could help trace the origins of this mysterious beast.

Investigators in the Badlands of Wyoming unearth the bones of a Mosasaur, a terrifying marine predator from the dinosaur age.

Dan O'Neill is on a mission to save the snow leopard. In Kyrgyzstan, there's a snow leopard that has never encountered humans. And in Mongolia, he tracks down the largest snow leopard ever recorded.

The hunt for the largest snow leopard, 'The Dude', heats up. With each revelation, Dan and his team grapple with the complexities of snow leopard behaviour.

Gujarat in India is home to the last Asiatic lions in the wild; a first-time mother lioness must be creative in her survival skills to raise a new king, and that includes fooling the old one.

Told through the experiences of its native species, this is the moving story of the changing fortunes of New Zealand's wildlife since humans first arrived.

The Great Barrier Reef, a series of coral reefs along Queensland's coast, is the largest structure created by organisms. It changes with the tides, the seasons and shaping forces such as erosion.