Mine is NASDS. There are different vendors who certify divers. I was a ocean Lifeguard in San Diego years ago, there was an instructor who was a danger to all of his students. He didn't use common sense and took his classes out in rough water unnecesarily. One time, he and his entire class had to be rescued coming back into the cove. It doesn't matter what cert you get as long as you have a competant instructor who can show you how to be a safe diver.