Scientists believe that there are over 1 million species of animals and plants living in the ocean. Some speculate that there are 9 million species that have not yet been discovered.
Animals that live in the ocean come in many different shapes, colors and sizes and live in even the coldest and deepest environments in the ocean. For example, tubeworms live in hot sea vents, which are one of the most extreme environments in the ocean. The largest animal in the ocean and in the world is the blue whale, which lives side by side with one of the tiniest marine organisms, plankton.