The Professional Association of Diving Instructors (PADI) is the world's largest recreational diving membership and diver training organization founded in 1966 by John Cronin and Ralph Erickson. Cronin was originally a NAUI instructor who decided to form his own organization with Erickson, and to break diver training down into several modular courses instead of the single universal course then prevalent.
PADI courses range from minimal entry level to relatively advanced recreational diver certification, several specialized diving skills courses, usually connected with specific equipment or conditions, some diving related informational courses and a range of recreational diving instructor certifications. Under the PADI TecRec brand, they also offer various technical diving courses. PADI's sister company Emergency First Response Corp provides a range of first aid and CPR programs for lay people, including workplace specific programs in Australia, Canada and the UK. As of March 2017 PADI is reported to have issued 25 million scuba certifications.