Under the sea, the reproduction chain is extremely varied and complicated. How are marine animals able to reproduce in such vast, dark oceans where meeting a partner seems impossible? How, in this moving, liquid element, do they manage to overcome the challenge of perpetuating the species? Over millions of years of evolution, marine animals have used the physical properties of the water, each in their own way, and succeeded in developing original mating strategies for passing on their genes. (From France, in English) (Documentary) PG