An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. Some examples of invertebrates are coelenterates. This phylum consists of jellyfish, anemones, corals, and hydras. Another type of invertebrate aquatic animal is the annelids which are segmented worms. There are three different classes they are polychaetes, oligochaetes, and hirudinea.