The oceans cover two-thirds of the planet's surface, yet they are still largely unexplored. For animals that live on the surface or in the deepest abysses, the most difficult task is finding food and conserving energy. Planet Earth's cameras travel across the vastness of the planet to show how high the stakes are to survive in this boundless, fruit-poor environment. Once upon a time, anyone who lost their legs in an accident was handicapped for life. Today there is a young man who walks and runs with prosthetics. He is Oscar Pistorius. Much has been said about him, but less about his legs: they are a prodigy of technique and craftsmanship and the laboratory that produced them is located in Iceland. Francesca Marcelli went to visit this refined technological workshop. Becoming an athlete for the Olympics is the sum of many factors: a suitable constitution, lots of training, but also a particular determination and the commitment to keeping your biological machine in full efficiency.