Acorn barnacles can stick to almost any firm surface - a ship's hull, seashells, piers and pilings, rocks, the skin of whales and sea turtle shells. A roughened surface provides the most favored anchorage. On fixed objects they tend to settle in relation to light, water current and contour of the surface, but water movement is the primary factor in the positioning of barnacles as they set. They live mainly in tidal zones. Gooseneck barnacles favor floating objects in the sea, such as logs, debris and sea turtles.
Parasitic barnacles can be very selective in their choice of habitat.
Some bore only into the shells of sea turtles and are missed by the casual observer. Others will only attach to certain crabs. Some species may only be found boring into the shells of conchs. The parasites may not be easily recognized as barnacles, since their body structure is modified for their special role in nature. However, without access to the specific host they are adapted for, they will not survive.