CRUSTACEA/CIRRIPEDIA
The most familiar members of the class Cirrepedia, barnacles are exclusively marine animals. As adults, they are sessile (nonmoving). After molting several exoskeletons while swimming freely in their developing stages, barnacles attach themselves as adults to inanimate objects such as rocks, shells, and the bottoms of boats and ships— in addition to animals such as turtles, fish, whales and coral.

Many barnacles use their antennae as an attachment organ. Their body is surrounded by pairs of fixed calcium-rich plates and is protected by another pair of plates that close the body opening.

As suspension filter feeders, barnacles use their six pairs of thoracic legs to "kick" small bits of food and plankton filtered from the water into their mouth.