Light through the water descends to the bottom of the sea. Ocean floor - the surface of the lithospheric plate, which is covered by the waters of the oceans. The underwater topography is as diverse as the topography of the continents. There are ridges, crevices and valleys. The main parts of the bottom are the shelf, the continental slope, the bed of the ocean, deep troughs, mid-ocean ridges, underwater basins, oceanic plateaus.