UNEP. A book on the special places of the world's oceans; Ecologically and Biologically Significant

The ocean encompasses 71 per cent of the planet’s surface and a large portion of its habitable space. Whereas life on land is almost exclusively contained within a thin strip of breathable atmosphere overhead, in the ocean it is found from the waves that wash against the shore to the deepest canyons that plunge thousands of metres beneath the sea floor.