Turtles are the only reptiles with a shell. Some turtles can pull their head, legs, and tail into the shell for protection. There are about 250 species of turtles. They live on land, in fresh water, and in the ocean.f air temperatures do not suit them, some reptiles can hibernate until the temperatures are right again. Another unique characteristic of reptiles is their eyes. The shape of a reptile's pupil, the black spot in the center of the eye, indicates whether the animal is active at night or during the day.