In the third episode, prominent adventure sports photographer Krystle Wright captures the immersive world of free-diving in Vanuatu, athletes who appear to walk on air in the canyons of Colorado, and powered para-gliders on the flooded salt pans of Utah.

Laurent Ballesta has yet again challenged himself to a new world record: spend 28 days at a depth of 100 meters to reveal the luxuriant and unknown depths of the Mediterranean.
Because people have been travelling there for thousands of years, this sea is be­lieved to be without secrets. And yet, far below its surface, lie vast unexplored territories, luxurious gardens worthy of the finest tro­pical coral reefs. These natural wonders are inaccessible to the traditional diver, in a twilight zone, between 60 and 120 m, where there’s less than 1% of sunlight. If diving at such depths is always a challenge, staying there is a fan­tasy, a utopia that becomes reality in 'The Deep Med'.

(Click CC for subtitles) Descending to remarkable depths below the sea on one single breath, Alessia Zecchini enters what she describes as the last quiet place on Earth. The Italian champion is determined to set a new world record in freediving, a dangerous extreme sport in which competitors attempt to reach the greatest depth without the use of scuba gear. Freedivers are often subject to blackouts upon ascent, necessitating the help of safety divers like Stephen Keenan, a free-spirited Irish adventurer who fell in love with the sport in Dahab, Egypt.
Having formed a special bond on the freediving circuit, Alessia and Stephen train together to make an attempt on Dahab’s legendary Blue Hole and its challenging 85-foot-long tunnel 184 feet below the Red Sea, their fates inextricably bound together.

Every summer in the seas off Alaska humpback whales, sea lions and killer whales depend on an explosion of plant life, the plankton bloom. It transforms these seas into the richest on Earth. But will these animals survive to enjoy the great feast? The summer sun sparks the growth of phytoplankton, microscopic floating plants which can bloom in such vast numbers that they eclipse even the Amazon rainforest in sheer abundance of plant life. Remarkably, it is these minute plants that are the basis of all life here. But both whales and sea lions have obstacles to overcome before they can enjoy the feast. Humpback whales migrate 3,000 miles from Hawaii, and during their 3 month voyage lose a third of their body weight. In a heart-rending scene a mother sea lion loses her pup in a violent summer storm, while another dramatic sequence shows a group of killer whales working together to kill a huge male sea lion.
In late summer the plankton bloom is at its height. Vast shoals of herring gather to feed on it, diving birds round the fish up into a bait ball and then a humpback whale roars in to scoop up the entire ball of herring in one huge mouthful. When a dozen whales work together they employ the ultimate method of co-operative fishing - bubble net feeding. One whale blows a ring of bubbles to engulf the fish and then they charge in as one. Filmed from the surface, underwater and, for the first time, from the air, we reveal how these giant hunters can catch a tonne of fish every day.

The second programme deals with the mechanics of flight. Getting into the air is by far the most exhausting of a bird's activities, and Sir Attenborough observes shearwaters in Japan that have taken to climbing trees to give them a good jumping-off point. The albatross is so large that it can only launch itself after a run-up to create a flow of air over its wings. A combination of aerodynamics and upward air currents (or thermals), together with the act of flapping or gliding is what keeps a bird aloft. Landing requires less energy but a greater degree of skill, particularly for a big bird, such as a swan. Weight is kept to a minimum by having a beak made of keratin instead of bone, a light frame, and a coat of feathers, which is maintained fastidiously. The peregrine falcon holds the record for being fastest in the air, diving at speeds of over 300 km/h. Conversely, the barn owl owes its predatory success to flying slowly, while the kestrel spots its quarry by hovering. However, the true specialists in this regard are the hummingbirds, whose wings beat at the rate of 25 times a second. The habits of migratory birds are explored. After stocking up with food during the brief summer of the north, such species will set off on huge journeys southwards. Some, such as snow geese, travel continuously, using both the stars and the sun for navigation. They are contrasted with hawks and vultures, which glide overland on warm air, and therefore have to stop overnight.

The Red Sea is one of the youngest oceans in the world and one of the warmest. The northern region, with its diverse array of marine life, is one of the most visited dive locations on earth while the southern end remains virtually unexplored. It's a global hotspot for marine biology and an important trade route throughout human history, linking the trade goods of India and the Far East with the markets of Egypt and Europe.