Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
All depends. I started in the sixties,there were no AWO certs then, just a scuba cert. I've been diving 40 years without any additional certs. I've been able to dive anywhere, anytime. So necessary? These days I'd say yes because in the OW class all you learn is how not to kill yourself. Or a resort 2 day or 4 day class even less. My course was 12 weeks 2 nights per week 2 hours per night session. We learned enough to be able to advance through diving which IMO is when you learn how to dive.