Oceans are the largest ecosystem in the world, and oceans covers 70% of the world. There is the Euphotic, bathyal, and the abyssal zone. In the Euphotic zone animals like plankton live there, in the bathyal has almost no light or absolutely no light what so ever. In the abyssal and the pressure there can crush you flat, and it is completely dark. There are many different type of animals in each zone.Corals are made made of dead animals, and can support many different small fish. And the ocean floor is not flat it has cliff and mountains.