They float at or near the ocean's surface when there is sunlight, drifting with the currents and tides:

They are the main food for many larger organisms, like whales:

They are the group of animals that can swim:

They can look for their own food and swim away from another animals:

They are found in most areas of the ocean and stay where the conditions best suit them:

Some of them can live in places where there is really high water pressure and no light, like in an abyss:

This creatures live on the ocean floor and shore areas:

They have external skeletons: