Sea turtles are one of the Earth's most ancient creatures. The seven species that can be found today have been around for 110 million years, since the time of the dinosaurs. The sea turtle's shell, or "carapace" is streamlined for swimming through the water. Unlike other turtles, sea turtles cannot retract their legs and head into their shells. Their color varies between yellow, greenish and black depending on the species.
Green sea turtles spend most of their lives underwater, where they can rest for up to five hours at a time before coming up for air. When active, they typically alternate between being underwater for a few minutes and coming up to the surface to breathe air for a few seconds. Green sea turtles are also known to sunbathe on land.
