Intertidal zone along a beach
In the sea, creatures swim, float, crawl around the bottom, or glue themselves to something solid like a rock or burrow. Plants float or hang onto something solid or are fixed into sand. Animals can live anywhere in the sea, but plants must have light to produce food. In clear seawater it starts becoming very dark once you go below 50 metres. Most of the plants in the sea are microscopic algae. They are eaten by microscopic animals called zooplankton.
Most animals living deeper in the sea live on food that sinks down to the bottom or the other creatures that also live down there. Have you seen pictures of some of the bizarre creatures in the bottom of the sea?