The green sea turtle gets its name not from the color of its shell (which is typically brown, gray, black and yellow) but from the greenish shade of its fat. A serrated beak helps these herbivores tear through vegetation. Their shells, which are lighter and more hydrodynamic than those of terrestrial turtles, allow them to glide easily through the water, while flippers enable them to swim long distances. Male sea turtles spend their entire lives at sea, but females return to the same beaches they were born on, once every two years or so, to lay eggs.