(Click CC for English subtitles) Four Finnish cave divers face their worst nightmare when two of their friends drown deep inside an underwater cave in Norway. When the official recovery operation is called off by the Norwegian and British authorities after being deemed too risky, the friends set out on a secret mission to retrieve the bodies themselves. "Diving into the Unknown" isn’t just the dramatic story of a life-threatening mission. It is also a story about unconditional friendship that truly runs deep. While each member of the team has years of experience exploring dangerous deep-sea caves, together they are about to face the biggest challenge of their lives. To make it out alive, they will need to be able to rely on each other every second of the way. And the physical demands of this operation will pale in comparison to the psychological toll it will take on everyone involved. With footage from the actual accident and multiple cameras both above water and deep below the surface, this film follows the breathtaking recovery mission from beginning to end.

Ideas about time and space are explored in the changes that constellations undergo over time, the redshift and blue shift measured in interstellar objects, time dilation in Albert Einstein's theory of relativity, the designs of both Leonardo da Vinci and spacecraft that could travel near light speed, time travel and its hypothetical effects on human history, the origins of the Solar System, the history of life, and the immensity of space. In Cosmos Update, the idea of faster-than-light travel by wormholes (researched by Kip Thorne and shown in Sagan’s novel Contact) is discussed.

Long ago, two species of human beings coexisted on Earth until competition drove one of them to extinction. This program, set in the southwest of France 35,000 years ago, reconstructs the life in the Neanderthal world at the time Cro-Magnons first entered the scene. All aspects of Neanderthal clan life are examined, including tool- and weapon-making, hunting and gathering, health and healing, childbirth, rituals, and making fire. Footage of skeletal remains and the scholarly research of eminent paleontologist Chris Stringer and Oxford University's Paul Pettitt support the documentary.

Heart disease is the number one cause of deaths worldwide, killing more than eight million people each year. Cardiac infarction, more commonly known as a heart attack, can happen without warning, killing heart muscle cells immediately. Even if the patient recovers, the damage to their heart may not.
But there are researchers frantically working to change that. Meet the people inventing the future of cardiac health, from new ways of imaging the body, to the possibility of 3D printing a functioning heart.

Reptiles and amphibians look like hang-overs from the past. But they overcome their shortcomings through amazing innovation. The pebble toad turns into a rubber ball to roll and bounce from its enemies. Extreme slow-motion shows how a Jesus Christ lizard runs on water, and how a chameleon fires an extendible tongue at its prey with unfailing accuracy. The camera dives with a Niuean sea snake, which must breed on land but avoids predators by swimming to an air bubble at the end of an underwater tunnel. In a TV first, Komodo dragons hunt a huge water-buffalo, biting it to inject venom, then waiting for weeks until it dies. Ten dragons strip the carcass to the bone in four hours.

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.