Hi eijnaix, to answer your questions, the Open Water Diver course, if you complete it successfully, does confer a certification as an Open Water Diver. With this certification, you can dive anywhere in the world as a "fun diver." Different schools follow different schedules, but the way I teach it, we have two days with half a day of classroom sessions and half a day of swimming pool sessions, and two days with diving in the ocean, from a boat. So all in all, four days for the course, and whatever time it takes you to study the material on your own (I expect students to come to class prepared). I don't recommend shorter courses than that because it usually means rushing through the pool sessions and the classroom sessions.