Beautiful seashells that are washed ashore on beaches by ocean waves have always amazed people. Shells come in a collection of shapes, sizes, and colors. Shells are actually made by marine creatures to serve as their homes. Seashells are, quite simply, skeletons of mollusks. Mollusks are a class of water animals that have soft bodies and hard outer coverings, called shells. People have bony skeletons on the inside and soft bodies on the outside. But mollusks do just the opposite. Shells protect these soft-bodied animals from rough surfaces that can harm their bodies. Shells also protect mollusks from predators.

Shells are durable and last longer than the soft-bodied animals that make and wear them. Shells may be univalve or bivalve. Univalve shells are made up of just one unit. Bivalve shells have two units or two halves. Snails have univalve shells and oysters have bivalve shells.

The main role of a sea shell is: