standards of fitness to dive, and persons authorised to perform medical examinations on divers to assess their fitness to dive. Formal registration of personnel assessed as competent to perform in specified roles as members of a professional diving team, and their legal responsibilities in terms of occupational health and safety. In most jurisdictions, recreational diving is unregulated, and an entirely untrained person is not legally hindered from scuba or freediving at their own risk in public access bodies of water. There is to some extent industry self-regulation, and most service providers will require customers to show evidence of competence appropriate to the service requested. This is usually a matter of presenting a recognised C-card, and is intended mainly to limit liability. The other instrument commonly used to limit liability is a waiver signed by the customer as part of the conditions of service. Exemptions In special cases exemptions may be granted for specific classes of diving operations, or for specific diving projects. USA – Depending on state legislation, public safety diving in the USA may fall under state or federal occupational safety and health legislation. Federal legislation applies where there is no relevant state legislation and the divers are employees diving as part of their occupation. If they fall under federal legislation they are exempt (excluded) from specific requirements of 29 CFR Part 1910, Subpart T, Commercial Diving Operations, only during diving activities incidental to police and public-safety functions the purpose of which is to provide search, rescue, or public-safety diving services. The exemption was written to include the ability to deviate from safe diving practices under limited conditions where compliance would be impracticable due to time constraints or the possible consequences of failing to perform the task overwhelm the risks taken using available facilities. This exclusion does not apply during training, recovery operations, searches where there is no reasonable probability of rescue of a living person or there is no real and immediate public safety hazard. The specific federal legislation does not apply to volunteers where there is no employer/employee relationship. Scientific diving in the US is also exempt from 29 CFR Part 1910, Subpart T, Commercial Diving Operations provided that such diving is under the auspices of the American Academy of Underwater Sciences, and complies with all requirements for the exemption, which are tied to the AAUS Standards for Scientific Diving Certification and Operation of Scientific Diving Programs.