The Diamondback Terrapin ranges from 5-10 inches (12.7-25.4 cm) in carapace length. The diamondback terrapin's carapace color varies from a brown-ebony to a darker, almost black. On the carapace, each scute has multiple "diamond-shaped" rings which may be the origin of this species' name. The turtle's skin can range anywhere from dark gray to stark white, which is complimented with black irregular spots. Males are often very darkly colored, and sometimes have black markings on their upper jaw, resembling a mustache.
Diamondback terrapins can be found along the coast of Georgia. They are most common in salt marshes and shallow bays. They are usually found in brackish water and occasionally travel out into the open ocean, however, they cannot tolerate full-strength salty water for long periods of time, or they may dehydrate.
Although diamondback terrapins are an aquatic turtle and spend the majority of their life in water, they do leave the water to bask and lay eggs. One adaptation these turtles have acquired over time is the ability to survive in salt waters of variable salinities. Like sea turtles, diamondback terrapins posses salt glands around their eyes, allowing them to secrete excess salt from their blood, and survive in salty environments.