Going down into these narrow flooded passageways is not for the faint-hearted but, with only an estimated one percent of the caves explored, it is an opportunity for the team to write themselves into cave diving history, by pushing further in than anyone has before. This is a challenge that tests even the most accomplished cave divers. Steve must face the terrors of being lost in an underwater silt cloud in a cave. But there is a bigger issue at stake. All life in the Yucatan depends on the fresh water in this network of caves, but it's being contaminated by human development. With every metre the team maps, it adds to the knowledge of the system, which, in turns, helps protect it for future generations.
Todd trains hard to improve his body intelligence, visualization skills, and emotional intelligence before attempting a super-human feat. He faces his greatest fear - being chained, handcuffed and blindfolded underwater with only his radically improved brain to help him escape.
Sir David Attenborough tells the stories of the world's best animal architects. There are house-proud bower birds, who only find a mate if they decorate their homes perfectly. There are hornets, who build electric central heating systems, and the star-nosed mole, whose house is designed so well that worms, his favourite meal, literally drop in for dinner. From larders to nurseries and from high-rises to subway systems, Attenborough shows that the animal architects have designed it long before humans.
The Orange River travels almost two-thirds the length of South Africa to reach its most scenic checkpoint: The mighty Augrabies Falls. Widely regarded as one of the six great waterfalls on Earth, it is also an interminable source of hydration and food for the wildlife that live near its waters.
In the wilds of the Canadian Rocky Mountains, a mother moose tends to her newborn calf. Spring is in full swing, but this far north, winter is never far away and, with hungry bears and wolves for neighbours, many challenges lie ahead. Local cameraman Hugo Kitching knows this only too well, but he is determined to follow the mother and calf through the four seasons. What unfolds is a very intimate story, and when Hugo finds a second moose calf born late in the year, things take an unexpected and dramatic turn.