Sea turtles travel far and wide, riding currents across the open ocean. Females return to the same beach each year, using magnetic clues as a map back home. Under the cover of darkness, the mother climbs onto the beach to lay close to 100 eggs each. She then buries them under a sandy blanket and returns to the sea.
After about two months the eggs hatch. On a mad dash for the sea, newly hatched sea turtles scurry to escape animals that want to eat them.
For turtles, shells are natural suits of armor that protect them from predators. Sea turtles can't draw their arms, legs and heads into their shells, but their large size and scaly, tough neck skin also help protect them from predators.
Over millions of years, the forelegs of sea turtles have changed to flipper-shaped blades, which help them "fly" through the water—sometimes as fast as 15 miles (24 km) per hour. Sea turtles use their hind feet as rudders.
Instead of teeth, these turtles have sharp beaks, which allow them to cut and tear their food. Sea turtles can drink sea water because they have glands near their eyes that remove excess salt.
Sea turtles face many threats, including loss of nesting beaches due to development, hunting, egg harvesting and pollution. They're also caught accidentally as bycatch, though the fishing industry has developed "turtle excluder devices," trap doors in shrimp nets that allow turtles to escape. The green sea turtle is on the red (endangered) list of the International Union for the Conservation of Nature and Natural Resources (IUCN).
But soon they'll face even bigger challenges. As oceans warm and sea levels rise, sea turtles will struggle to find enough food, mates and nesting beaches. And rising temperatures could also upset the balance of male and female turtles. Warmer eggs become females, while cooler eggs become males. If beaches get too warm, scientists worry there could be too many females—and not enough males to fertilize their eggs.
Green sea turtles get their name from an internal layer of green fat.
Many islands around the world are known as "turtle islands" because they host nesting green sea turtles.
Green sea turtles can live to be 80 years old.
Sea turtles breathe oxygen, but can stay underwater for up to two hours before coming to the surface and taking one explosive breath.
Sea turtles rid themselves of excess salt through a "salt gland" near each eye, making them appear to be crying.
Turtles are reptiles, related to snakes, crocodiles and now-extinct dinosaurs.