what are barnacles
Barnacles are encrusters, attaching themselves permanently to a hard substrate. The most common, acorn barnacles (Sessilia), are sessile, growing their shells directly onto the substrate.The order Pedunculata ( goose barnacles  and others) attach themselves by means of a stalk.arnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile (nonmotile) suspension feeders, and have two nektonic (active swimming) larval stages. Around 1,220 barnacle species are currently known.