Worldwide there are hundreds of scuba training agencies. PADI, NAUI, IANTD, SSI, YMCA, NASDS, TDI, PSA, BSAC, just to list a few. No training agency is “absolutely” the best. Some agencies are highly visible and focus on marketing. Other training agencies focus on the theory and academics of sport diving, skill performance, and safety. There are agencies whose training is military in style. You may want a dive instructor who is certified by 2 or more training agencies to get a more rounded experience and education. If you are certified by a recognized training agency, such as the above, you may dive at any resort location worldwide regardless of affiliation.