A green sea turtle is most easily recognized by its top shell. The shell covers most of the animal’s body, except for its flippers and head. Despite its name, a green sea turtle's shell is not always green. The smooth, heart-shaped shell can be a blend of different colors, including, brown, olive, gray, or black. The underside is a yellowish-white color. The green sea turtle’s head has brown and yellow markings.

Green sea turtles have paddle-like limbs called flippers that allow the turtle to move quickly and easily through the water. These dense, heavy animals can reach three to four feet in length and weigh upward of 300 to 350 pounds (136 to 159 kilograms). Despite their size, they are still not the world's largest sea turtles—that title belongs to the leatherback sea turtle.