Females mature at about 12 years, and can weigh up to 7 pounds and and reach a length of 9 inches. Diamondbacks live in brackish and coastal waters and marshes. Their webbed feet make them agile swimmers and sharp claws help them move about the marshes. They eat clams, snails, worms, crabs, insects and fishes. Diamondbacks usually mate in May, and always mate in the water, usually at night.
Females can store sperm and produce fertilized eggs up to four years after mating.
They lay their pinkish, leathery eggs in June and July in nests dug out of sandy beaches or marsh edges above the high tide line. An average nest will contain about 13 eggs. Eggs hatch between August and October. A very late hatch, though, may cause hatchlings to overwinter and hibernate in the nest and emerge the next year. As with most turtles, temperature is believed to influence the sex of the hatchlings.