An ocean of living beings…

This paper will expose the state of the art concerning the ocean, both a unified entity and composed of several seas Our knowledge of its connectivity, salinity and stability in space and time will be highlighted. Physical, chemical and biological aspects are also broached. The exploitation of mineral and living resources by humans is presented. Today the ocean is threatened for the destruction of coastlines, generalized contaminations, over-exploitations of all kinds of resources, the dissemination of invasive alien species and the acceleration of the climate change. Finally, there are developments on biomimicry and the value of ocean.