A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. They are sessile (non-motile) suspension feeders, and have two nektonic (active swimming) larval stages. Around 1,220 barnacle species are currently known. The name "Cirripedia" is Latin, meaning "curl-footed".
Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings.
Washed up on the beach in the Florida panhandle.