Shell Jewelry Guide:- The marine environment is home to many different animals. One of the most interesting marine animals that live in the ocean is the mollusk. These marine animals generally have a hard, protective outer layer, or exoskeleton called shells. Some of the mollusks that make shells are whelks, conchs, clams, winkles, limpets, and cowries. An interesting fact: the empty shells that you find on beaches can be hundreds, or even thousands of years old – so remember – each shell you find on the beach is a piece of history.