A bobber in a harbor is an object used to mark the location of a BUOY or CORK. It is typically a brightly colored float that is attached to a rope or chain and anchored to the seafloor. The bobber is used to indicate the presence of a BUOY or CORK, which can be used to mark a specific area or provide navigational guidance. It is also used to indicate the presence of a fishing net or other type of fishing gear. The bobber is an important tool for fishermen, as it helps them locate their nets and other equipment quickly and easily.