The barnacle's free swimming larvae attach to almost any solid surface where they form a hard shell and remain there for the rest of their lives. They are often seen on dock pilings, rocks as well as the hulls of ships.
Many people mistakenly belive that barnacles are some type of mollusk because of their sessile nature and hard shell of calcium carbonate. They are actually crustaceans and are more closely related to crabs and shrimps. Barnacles feed by using their feathery feet to brush plankton and organic matter into their mouths.
Barnacle attached to a blue mussel shell.