Leatherbacks are the largest turtles in the world. They are called such bc they do not have a hard shell. Bc of the depth they dive, water pressure is great; therefore, the plasticity in the shell is necessary. Some can be the size of a VW Beetle!! Unfortunately they are disappearing at an alarming rate due to few and unenforced protection laws. Estimates are that they will be extinct within 20-30 years.