Planet Earth is an ocean planet. We can hardly ignore the fact that the ocean covers almost two thirds of our planet. Since the dawn of time, humankind has had an ambivalent relationship with the immensity and hostility of this very specific environment. However, the ocean holds a strong attraction for human societies, with nearly 40% of the world’s population living less than 100 km from the coast and most of the world’s big cities built on the edge of the ocean. However, the connection between humankind and the ocean runs much deeper than simple geographic closeness. The ocean plays a crucial role in the climate of our planet. It exchanges significant quantities of energy and water with the atmosphere. It distributes energy from the tropics to higher latitudes, warming the polar regions and cooling the tropics. It also helps define the characteristics of regional climates by influencing air temperature and rainfallamounts.