Six of the seven species of sea turtles that swim the planet’s waters—leatherback, loggerhead, Kemp’s ridley, green, olive ridley, and hawksbill—are found in every ocean except the Arctic and Antarctic. The seventh, the flatback, lives only in the waters around Australia.

The leatherback is the largest sea turtle and can weigh a whopping 2,000 pounds. It’s also the only sea turtle that doesn’t have a hard, bony shell. Its carapace is somewhat flexible and almost rubbery to the touch. The shells of other sea turtles are made of thick plates called scutes.

Sea turtles make incredibly long migrations between feeding and breeding areas. The leatherback travels an average of 3,700 miles each way. Sea turtles mate at sea,