Sea turtles belong to an ancient group of reptiles. Their bodies are enclosed by an armor-like shell, or carapace, that is fused to the backbone. Unlike land tortoises and turtles, sea turtles cannot retract their heads into the shell. Their legs, the large forelimbs, are modified into flippers for swimming.

Their shells may grow to 40 in in length. They feed mostly on seagrasses and seaweeds. Green turtles lack teeth, but they have strong biting jaws.Their diet consists largely of jellyfish. All the sea turtles must return to land to reproduce.