First, I really hate having this discussion, but always seem to get drawn into it to correct incorrect or misleading statements.
Second,
none of the agencies are perfect.
Third, we often hear, "the instructor, not the agency makes the biggest difference between classes." While true, it is a misleading statement. The agency, in most cases, provides the basis for what the instructor does or does not teach. You cannot teach what you've never learned. The vast majority of instructors neither cut corners nor add material to their classes, they teach their agencies standards - no more, no less. This makes the agency's standards far more important than some would have you believe. Some agencies leave certification up to the discretion of the instructor, while others require an instructor to certify divers who've completed minimum standards
even if the instructor feels the student would be an unsafe diver.Next, often people will bring up the Recreational Scuba Training Council (RSTC) or recently, the World Recreational Scuba Training Council (WRSCT), telling how they set standards for all agencies and therefore all agencies have the same standards. This is simply not true. While the RSTC does set
minimum standards for the industry, it is not true that it set standards for individual agencies. All agencies are not members of the RSTC, only members are required to follow RSTC minimum standards. For those agencies who are members, the RSTC sets
minimums, all members are free to exceed thos minimums. For example, the RSTC eliminated swimming requirements for the Open Water (OW)course. The swimming requirements were replaced with a requirement that an OW student either be able to swim 200 yds (183 meters)
or be able to snorkel 300 yds. This must be completed prior to certification. This opens SCUBA training up to non-swimmers. Yes, you can snorkel 300 yds without being able to swim at all. As far as I'm aware, only PADI has adopted that identical minimum requirement. YMCA, for example requires a 200 yds swim before I can even begin in water training. It requires a 300 yd swim prior to certification. This not merely the first of many examples of differences in training and philosophy. In the US, there are only 6 agencies who are members - IDEA, PADI, PDIC, SDI, SSI and YMCA. Peter, you can look
here for RSCT info. Next, there are differences in philosophy from one agency to another. One philosophy is:
Diving is fun and easy. It is possible to make the course easy as well if we eliminate skills that might possibly frighten anyone on their first day of class. If too many skills are included, it results in task loading which will interfere with a student learning necessary tasks and make them an unsafe diver.
A second philosophy is:
Diving is fun and easy. It is possible to make the course easy as well if we begin with simple skills, teach how to complete teach skill and allow plenty of practice time on each skill. Once a simple skill is mastered, other elements are added, allowing plenty of time to practice each element. When those added elements are mastered, still more elements are added in the same manner. By approaching skill development in this manner, we are able to teach quite complex skills in a manner that is easy for students. Skill which might seem frightening to a student on the first day of class are a logical and easy progression by the time those skills are presented in class. This gives a student confidence and the ability to solve problems without panic.
PADI follows the first philosophy, YMCA and NAUI follow the second. I'm not familiar enough with standards of other agencies to tell you which philosophy they follow.
Next, you'll often hear the concept, as we did earlier, that since PADI is the largest agency, they'll have the most poor divers as well asd the most good divers. I'm not sure what that point is aimed at proving, but it certainly does not address any real issues, it is merely a smoke screen designed to hide differences that do exist.
As Brian pointed out, SSI is the only agency (NASDS also had such a requirement, but merged with SSI in 1999) that requires it's instructors to be affiliated with a dive shop. The concept is that allows direct supervision of instructors to stop them from cutting corners. While the concept is a good one, there are three problems with it. First, there is no direct supervision of the instructor if he happens to be the shop owner. Second, the shop owner may or may not be an instructor. How is a non-instructor qualified to supervise instruction? Third, most pressure to cut corners in instruction comes directly from dive shops. I believe the fox was set to guard the henhouse.
So what happened?
The economic conditions of the late 1970's with interest rates over 20% put recreational activities, including diving, way down on priority lists. PADI decided to remove requirements, speed up training and make it much cheaper. Since we live in an instant gratification society, it was a tremendously successful marketing strategy. Prior to those changes, NAUI was by far the largest agency in number of divers certified, now PADI's certifications out number all the other agencies combined.