Terrapins are a type of small turtle that live in fresh or brackish water. They are not a taxonomic unit and may not be closely related, but many belong to the families Geoemydidae and Emydidae. The name "terrapin" comes from an Algonquian word that referred to the species Malaclemys terrapin, also known as the Diamondback terrapin. Terrapins are semi-aquatic and spend time both on land and in water. They tend to swim quite often, but also spend their time on land, basking in the sun and occasionally burrowing in the mud. Terrapins have a hard shell that is slightly streamlined yet also slightly domed, and they have legs similar to tortoises rather than flippers like turtles. Terrapins are omnivorous and their diet can consist of mollusks, small fish, crustaceans, insects, algae, and other aquatic plants. Unlike turtles and tortoises, terrapins remain relatively small. Terrapins require a varied diet and constant access to clean water, and they need a powerful filtration system to keep their water clean. While terrapins can make good pets, they require lots of care and equipment to keep them healthy for life.