Saltwater pearls are formed inside oysters that live in ocean waters. These pearls are created when an irritant, like a grain of sand, enters the oyster. To protect itself, the oyster secretes layers of nacre, a substance that eventually forms a lustrous pearl. The most common types of saltwater pearls are Akoya, Tahitian, and South Sea pearls. Each type varies in size, shape, and color, depending on the species of oyster and the environment in which they are cultivated. Saltwater pearls are highly valued in the jewelry market for their beauty and rarity.