some cases prescription drug use may have a net positive effect, when effectively treating an underlying condition, but frequently the side effects of effective medication may have undesirable influences on the fitness of diver, and most cases of recreational drug use result in an impaired fitness to dive, and a significantly increased risk of sub-optimal response to emergencies. Education and registration of practitioners Specialist training in underwater and hyperbaric medicine is available from several institutions, and registration is possible both with professional associations and governmental registries. Education Registration The American Medical Association recognises the sub-speciality Undersea and Hyperbaric Medicine held by someone who is already Board Certified in some other speciality. The South African Department of Employment and Labour registers two levels of Diving Medical Practitioner. Level 1 is qualified to conduct annual examinations and certification of medical fitness to dive, on commercial divers (equivalent to ECHM-EDTC Level 1. Medical Examiner of Divers), and Level 2 is qualified to provide medical advice to a diving contractor and hyperbaric treatment for diving injuries (equivalent to ECHM-EDTC Level 2D Diving Medicine Physician) Australia has a four tier system: In 2007 there was no recognised equivalence with the European standard. GPs completing the first tier four- to five-day course on how to examine divers for ‘fitness to dive’ can then add their names to the SPUMS Diving Doctors List GPs completing the second tier two-week diving medicine courses provided by the Royal Australian Navy and the Royal Adelaide Hospital, or the two-week course in Diving and Hyperbaric Medicine provided by the ANZ Hyperbaric Medicine Group, qualify to do commercial-diving medicals. The third tier is the SPUMS Diploma in Diving and Hyperbaric Medicine. The candidate must attend a two-week course, write a dissertation related to DHM and have the equivalent of six months’ full-time experience working in a hyperbaric medicine unit. The fourth tier is the Certificate in Diving and Hyperbaric Medicine from the ANZ College of Anaesthetists. Training of divers and support staff in relevant first aid Divers A basic knowledge understanding of the causes, symptoms and first aid treatment of diving related disorders is part of the basic training for most recreational and professional divers, both to help the diver avoid the disorders, and to allow appropriate action in case of an incident resulting in injury. Recreational divers A recreational diver has the same duty of care to other divers as any