SSI or Scuba Schools International - SSI is a worldwide diving training organization that specializes in business support for dive businesses that was established in 1970. It is, in fact, the largest school-based training agency in the world with various regional centers, and its certification is widely accepted throughout the world. They have a SSI Facility Search feature on their website if you need to get region-specific information.\012NAUI or National Association of Underwater Instructors - NAUI Worldwide was established in 1959 as a non-profit diving membership association, and organized solely to support and promote Dive Safety through education, which has now become the second largest diver training organization. Their training programs include Skin Diver through Instructor Course Director, with several specialty courses including Search and Recovery Diver, Scuba Rescue Diver, Nitrox and technical diving.\012PADI or Professional Association of Diving Instructors - Among the recreational diving membership organizations, PADI is the world's largest, with offices in Australia, Canada, Switzerland, Japan, Sweden, the United Kingdom, New Zealand and the United States. PADI started in 1967 and the main corporate headquarters is located in California, and is known as PADI Worldwide.