To have an idea about the magnitude of the problems involved in the analysis of the ocean resources, it is worth recalling the basic physical facts and figures. The world’s oceans cover about 71 percent of the planet’s surface, occupying an area of approximately 362 million km2, with an average depth of about 3,800 m and a total volume of 1,370 million km3 of water. Comparing the volumes of oceans and of dry land, the oceans provide 99 percent of the potential living space on Earth. Two-thirds of the oceans are located in the Southern Hemisphere. Given the oceans’ wide dimension, it is necessary to distinguish different scales on which the ocean affects human activities.