Sea snakes have flattened body with a short oar-like tail, small scales, nostrils on top of their head, and lungs that stretch the entire length of their body. Like all snakes, they have flexible jaws that allow them to eat food bigger than their head and no eyelids. Snakes belong to the group of animals called reptiles. Reptiles have a backbone, scales, breathe air and lay eggs. Reptiles also rely on their environment to warm or cool their body.