This page shows several species of sessile barnacles. Sessile barnacles are those that attach themselves permanently to a substrate and live their whole life within their shell. They feed by reaching into the water stream with their legs to catch passing food particles. The sessile lifestyle of barnacles makes sexual reproduction difficult since they can't leave their shells to mate. To facilitate genetic transfer between isolated individuals, barnacles have extraordinarily long penises. They also have the ability to change from male to female and back again. According to the book, Biology of Barnacles. Museum Victoria. Barnacles probably have the largest penis to body size ratio of the whole animal kingdom.
Barnacles are related to crabs and lobsters in the subphylum Crustacea. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings.
The Gooseneck Barnacles generally attach to floating objects, like buoys, ship bottoms and even plastic debris.
Welks feed on barnacles.
Acorn Barnacle Balanus sp.
Living with a broken shell.
Note the netted construction..