Jellyfish are free-swimming members of the phylum Cnidaria. They have several different morphologies that represent several different cnidarian classes and are found in every ocean, from the surface to the deep sea. Some hydrozoan jellyfish, or hydromedusae, are also found in fresh water. The freshwater species are less than an inch (25 mm) in diameter, are colorless and do not sting. Many of the best-known jellyfish, such as Aurelia are scyphomedusae, large, often colorful, and are common in coastal zones worldwide. There are approximately 1800 species, but the main three type of jellyfish are grape, apple and strawberry preserve.