Beachcombing is an activity that consists of an individual "combing" (or searching) the beach and the intertidal zone, looking for things of value, interest or utility. A beachcomber is a person who participates in the activity of beachcombing.
Despite these general definitions, beachcombing and beachcomber are words with multiple, but related, meanings that have evolved over time.
A seashell (or sea shell), also known simply as a shell, is a hard, protective outer layer usually created by an animal or organism that lives in the sea. Most seashells are made by mollusks, such as snails, clams, and oysters to protect their soft insides. Empty seashells are often found washed up on beaches by beachcombers. The shells are empty because the animal has died and the soft parts have decomposed or been eaten by another organism.
A seashell is usually the exoskeleton of an invertebrate (an animal without a backbone), and is typically composed of calcium carbonate or chitin. Most shells that are found on beaches are the shells of marine mollusks, partly because these shells are usually made of calcium carbonate, and endure better than shells made of chitin.
Scaphopoda (/skəˈfɒpədə/; from Ancient Greek σκᾰ́φης (skáphēs) 'boat' and πούς (poús) 'foot') is a class of shelled marine molluscs (invertebrates within the phylum Mollusca), whose members are known as scaphopods (/ˈskæfəˌpɒdz/) and commonly called tusk shells or tooth shells. They have a worldwide distribution and are the only class of exclusively infaunal marine molluscs. Shells of species within this class range in length 0.5–18 cm (0.20–7.09 in), with Fissidentalium metivieri being the longest. Members of the order Dentaliida tend to be larger than those of the order Gadilida.
These molluscs live in soft substrates offshore (usually not intertidally). Because of this subtidal habitat and the small size of most species, many beachcombers are unfamiliar with them; their shells are not as common or as easily visible in the beach drift as the shells of sea snails and clams.