Professional diving is diving where the divers are paid for their work. There are several branches of professional diving, the best known of which is probably commercial diving. Any person wishing to become a professional diver normally requires specific training that satisfies any regulatory agencies which have local authority, such as US Occupational Safety and Health Administration, United Kingdom Health and Safety Executive or South African Department of Labour. Due to the dangerous nature of some professional diving operations, specialized equipment such as an on-site hyperbaric chamber and diver-to-surface communication system is often required by law.