Green sea turtles are found in the Pacific, Atlantic, and Indian oceans. Despite that vast area, the turtles are sensitive to heat and cold; therefore, the turtles are limited to the warmer parts of the ocean. The turtles can be threatened or injured by rough waves, rocks, and marine predators.
Consequently, the green sea turtles have developed some key adaptations that increase an individual's chance for survival. A structural adaptation is their long forelimbs, which are paddle-shaped. These are ideal for swimming long distances and maintaining speeds while swimming. The shell also does not allow for retractile limbs. That kind of structure would actually impede swimming efficiency. The turtles also have powerful jaws that are beak-shaped. This is advantageous because it allows the turtles to eat a wide variety of species with little effort. The turtles are also ectothermic. This means that they can't regulate their internal body temperatures through chemical reactions the way that mammals can. The turtles are forced to regulate their body temperature by using the surrounding environment. The fact that they are ectothermic also means that turtles' metabolism is more dependent on the surrounding environment. This is actually advantageous, because it gives the turtles the ability to lower their metabolic rate so that they need less oxygen. This allows the turtles to stay submerged for extended periods of time in order to feed and avoid predators that would like to feed on the turtle. Green sea turtles have been known to stay underwater for up to five hours, with a heart rate as low as one beat per nine minutes. Sea turtles are also capable of exchanging their entire lung volume in a few breaths. This allows the turtle to spend minimal time breathing air from the surface.