New divers will quickly realize that there are many acronyms that stand for the various training agencies. Some of the big ones in this area are PADI (Professional Association of Diving Instructors), SSI (Scuba Schools International), NAUI (National Association of Underwater Instructors), SDI (Scuba Diving International), and IDEA (International Diving Educators Association). You will notice the absence of YScuba which ended their program a little over a year ago. Some of the leaders of the YScuba program began SEI (Scuba Educators International).
Many new divers and those considering diving find this alphabet soup very confusing. One question they are always asking is "which agency is best?" That is a very difficult question to answer, and if you search the web there is much debate. The reality is that no agency is better than another. If you find yourself amongst divers who were certified by different agencies you will learn that the skills learned were nearly the same. Many agencies are members of the RSTC (Recreational Scuba Training Council) which sets minimum standards for the member agencies, and agencies that are not members generally follow the same minimum standards.
The most important aspect of choosing where to take your class is not which agency, but choosing the best instructor. It is best to shop around and "interview" the instructor and find one you are confident about. There are many different styles of teaching, and you want to find the instructor that uses the style that suits your needs.