Shell Buckles are the perfect addition to any beachside look. A shell is the protective outer layer of a marine animal, which are often found empty and washed up on the beach. They are the exoskeleton of invertebrates and are typically made up of calcium carbonate or chitin. Although seashells are the most common type, there are also freshwater and land animals that have shells. Shells, whether from land or sea, have been used by humans for thousands of years. Add a statement shell buckle to a high waisted bikini for an oceanic element.