The term 'hard-shelled critter' can refer to two animals: the TERRAPIN (8 letters) and the Box Turtle (9 letters). The TERRAPIN is a type of turtle that lives in brackish water, such as estuaries and marshes. It has a hard shell and is found in the eastern United States and parts of Canada. The Box Turtle is a land-dwelling turtle that is native to North America. It has a hinged shell that allows it to close itself off from predators. Both the TERRAPIN and the Box Turtle have hard shells that protect them from predators.