PADI Advanced Open Water is really nothing more than building *a little* more diving experience by exposing an OW diver to other types of diving conditions, like for example deep diving, altitude diving, drift diving, boat diving etc. These are of course not the only ones but it serves to demonstrate my point. The navigation part really adds the beginnings of a skill that comes in handy for most divers as they become more confident and less focussed on whether they are doing it all right and more aware of their newly discovered underwater environment by forcing them to concentrate a little more now that they can dive on finding their way around their diving environment.
All of these dives on the AOW, it should be said, serve as *introductory glimpses* into skills that could be more deeply explored and developed by completing a specialty course in that particular skill of interest to the diver. So a deep diving specialty course would focus solely on deep diving and because the AOW student has already been exposed a little to the idea that nitrogen narcosis is a factor to consider in dives generaly deeper than 60ft in his/her AOW course, the specialty course then serves to build on that knowledge, focus and to specialize only on that skill.
The Advanced course is really a hands on course that serves to get people to learn about diving by doing the diving. It's like learning to ride the bike by getting on and riding it. This serves to show the OW diver that there is more to diving than just OW's how to descend or ascend properly, how to check your saturation pressure groups with dive tables, how to clear one's mask, or how to deal with an out of air emergency etc; it allows the OW diver to now choose which of these avenues of personal interest he/she fancies to explore further in later specialty courses and learn more of what they are interested in.
For PADI certifications the deep and underwater navigation are compulsory AOW dives since they are the two most likely to be encountered/needed by all divers and since deep diving introduces the concepts of nitrogen narcosis, which in itself is a relatively simple but very important concept to address in deep diving.
Classroom work then for AOW takes on the the form of only addressing what little theoretical knowledge there needs to be explained and understood by the students to successfully complete the "themed" dives for the certification in practioce. The real learning comes through diving the dives themselves. An underwater naturalist dive might for example include the exercise for my students to learn more about what characteristics they need to take note of if they encounter a new fish species they have never seen before so that they can go find out more about it later when they have completed the dive. This way they get to dive another dive for the diving experience itself, and also start learning about marine animals themselves, and hopefully find an interest in learning more about each wonderful creature we so often take for granted.
I can only speak from my experience in the PADI context, but I'd guess the other certifying agencies would pretty much look at things the same way?
