Fish scales are small, flat structures that cover the skin of most fish. They serve as a protective barrier against parasites and environmental hazards. Scales can vary in shape, size, and texture depending on the species of fish, with common types including cycloid, ctenoid, and ganoid scales. The scales are made primarily of a protein called collagen and can also contain minerals like calcium and phosphorus. In addition to protection, fish scales can help reduce drag while swimming, allowing fish to move more efficiently through water. Some fish, like sharks, have a unique scale type called dermal denticles that further enhances their swimming ability.