Its extraordinary dimensions, as long as 15 metres, and shape in the form of a silver ribbon, inspired the myth of the sea serpent. For the past two years, scientific buoys, immersed at a depth of two thousand metres in the Mediterranean have attracted countless species of pelagic fish; among them, the Giant Oarfish drifting vertically, alone or by pairs. With the help of the world expert in Giant Oarfish and logistic collaboration of enthusiasts, a scientific expedition reveals the biology of this enigmatic ambassador of the abyss. Entirely shot in HD, the film raises the veil on its paradoxical habits: why do all the adults self-mutilate and rid themselves of two-thirds of their bodies without being affected? How do they meet in the immensity of the ocean? Why does this fish not have any known predators?