Sea turtles are from the superfamily Chelonioidea and are reptiles of the order Testidines. They have a more fusiform body, which means the middle of their body is wide and it tapers on body ends. This means that sea turtles cannot retract their head and limbs into their shell because of the lack of volume, however the shape allows them to be more hydrodynamic. Sea turtles can be found in all oceans except the polar regions.