Martina Amati brings her love of freediving to the film Under (Depth). Using only a single breath, she swims down into the ocean: ‘I let go of everything and enter a totally new world where I need to find my stillness in order to consume as little oxygen as possible. It is a form of meditation’.

While human beings may have evolved in water, for us this environment is extreme. At ten metres below the surface the atmospheric pressure doubles. As the body cools, ancient systems are activated to prioritise the delivery of oxygen to key organs. A guide line, also used to measure depth, plays out before the diver like an umbilical cord, stretching between the sunlit surface and the shadows beneath.