The Professional Association of Diving Instructors (PADI) is the world's largest certifying agency. PADI was "born" in 1966 and its parents are John Cronin and Ralph Erickson. PADI's roots, however, go farther back.
Erickson was a champion swimmer, lifeguard, and respected diver. As a Chicago diver, he was tempted to go through the Chicago YMCA's instructor certification but for various reasons he never went through the program. Then, in 1960, the National Association of Underwater Instructors (NAUI) held its first course during the Underwater Society of America convention in Houston, Texas. He became one of only a few to pass the week long marathon ICC. He returned to Chicago and began certifying divers under the NAUI name. Many of his trainees were those who couldn't complete the rigorous YMCA course.
Cronin was a manufacturers' representative for US Divers for the Midwest and Canada. Cronin and Erickson became acquainted through the Illinois Divers Association. They would discuss the possibilities of staring their own certifying agency but wanted to wait for the right time.
The night that the "time became right" was just after Cronin had driven from Chicago to Peoria, Illinois to give a lecture at a NAUI ICC. The trip was long, on bad roads, and takes three hours. When Cronin arrived to give his presentation he learned that the course had been cancelled. He was furious and the first thing he did when he returned to Chicago was to call Erickson and set up a time to meet.
On the following Tuesday night, they met at Erickson's apartment and formulated the new agency. It would be the first "for-profit" certifying agency. They bantered about names and formulated the name PADI Professional Association of Diving Instructors. After Cronin's experience, the word Professional was his main requirement. Erickson had a background in mechanical drawing so he drew the PADI logo with help from a friend of his.
The main new difference between the PADI program and that of LACO and NAUI was that PADI went away from the single course for certification. They developed the certification levels standard in the industry today.
As with all of the major agencies, PADI was not founded in a vacuum. They based some of their program on that used by other agencies but also developed new and innovative programs that would revolutionize the industry and help build them into the largest agency in the world. Erickson has left the day-to-day operations of PADI but Cronin remains at the helm of the agency.