Barnacles are small marine crustaceans that attach themselves to hard surfaces, such as rocks, ships, and even whales. They have a hard outer shell and are known for their unique feeding method, where they extend feathery appendages called cirri to filter plankton and other food particles from the water. These creatures are found in oceans worldwide, often in intertidal zones where they can withstand changing tides. Barnacles reproduce by releasing eggs into the water, where they develop into free-swimming larvae before settling down and becoming adults. Their ability to cling tightly makes them a common sight in coastal environments.