Many people think shells are like rocks, but in fact a shell is created by an animal called a mollusk. As the mollusk grows, so does the shell. Mollusks can be herbivores, carnivores or omnivores, but all need clean water habitats to survive. Shells mean many different things to many different people. Some people collect shells for crafts, some search for very specific shells for a collection, while others simply walk the beaches to observe and hear the sound of the shells amid their feet.