PADI was created in 1967 by John Crowin and Ralph Ericson. It is one of the largest and most popular recreational diver training organizations in the world. It brings together about 4000 dive centers in over 175 countries all over the world. Course materials are available in over 20 languages. PADI courses start at an introductory level and end with instructor ratings. Courses cover theory and practical application, they are the same all over the world. The participants easily learn theory mostly by themselves with the help of manuals and videos available for each course. Then the knowledge is reviewed with the instructor and at the end the participants take the final exam. Dives are conducted in confined and open water. The courses focus on diver safety and fun.