Filmed across four continents, Unbreakables takes eight super-fit members of the public on a punishing global trail to undergo a series of brutal challenges.
In settings ranging from the Norwegian arctic to the Sahara Desert, the volunteers learned to survive in the world's harshest environments and endured difficult military training.
After a week's training in Portsmouth, they go aboard HMS Belfast on nearby Whale Island and face simulations of both a sinking under heavy gunfire and a terrifying helicopter crash.
Taking them into the Sahara, they subject them to a series of gruelling challenges, including being buried alive, a 10-kilometre camel race, and an exhausting run over the sand dunes while wearing stifling gas masks.
After the first day, Carla suffers from dehydration and exhaustion, but must face her fear of water in a drownproofing challenge where the volunteers repeatedly sink in a pool with their ankles and wrists bound.
However, before they are deemed worthy of battle, the contenders must first prove themselves by stealing honey from wild bees, and participate in a body cleansing ritual.