Turtles are reptiles. Turtles live in the water and have flippers for swimming. Turtles can swim as fast as humans can run on land. They move their front flippers through the water like birds use their wings. Their rear flippers do the steering. Most turtles can pull their head, legs and tail into their hard shell for protection but sea turtles can't do this. A turtle's shell is made up of two bits. The bit that covers the back is called the carapace and the bit that covers the turtle's belly is called the plastron. A turtle's head is covered in hard scales. Turtles don't have teeth but they have a strong beak with a sharp edge so they can cut food like sea grasses. They have to go to the surface to breathe so if they get caught in underwater fishing nets they will drown. Turtles hatch from eggs. The females lay their eggs on land. They dig a hole in the ground, lay the eggs in the hole and then cover them with soil. The mothers then go away. The sun's warmth hatches the eggs. Female turtles hatch from the warmer eggs on top, males from the deepest and coolest eggs in the nest. When they are about 40 years old they will come back to the same beach to mate and lay their eggs. Some turtles can live to be over 100 years old.