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 and its specialised applications, offshore diving, inshore civil engineering diving, marine salvage diving, HAZMAT diving, and ships husbandry diving. There are also applications in scientific research, Marine archaeology, fishing and aquaculture, public service and law enforcement and military service. Any person wishing to become a professional diver normally requires specific training that satisfies any regulatory agencies which have regional or national 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.
The primary procedural distinction between professional and recreational diving is that the recreational diver is responsible primarily for his/her own actions and safety but may voluntarily accept limited responsibility for dive buddies, whereas the professional diver is part of a team of people with extensive responsibilities and obligations to each other and usually to an employer or client, and these responsibilities and obligations are formally defined in contracts, legislation, regulations, operations manuals, standing orders and compulsory or voluntary codes of practice. In many cases a statutory national occupational health and safety legislation constrains their activities. The purpose of recreational diving is basically for personal entertainment, while the professional diver has a job to do, and diving is necessary to get that job done.