At first glance, you might think it’s seaweed—but it isn’t that. Then you might wonder if it’s a sort of shell—but it isn’t that either. Actually, this spiral object contains a living creature! To be precise, it’s the former home of a sleeper shark embryo. These animals lay eggs that are enclosed in this spiral, which allows the female to shelter them away from predators. This protective envelope, made of a material similar to that of fingernails, forms inside the mother and surrounds the fertilized egg. Its structure allows it to stick to the ocean depths.