Interestingly enough, two very old and dear friends of mine live in California, and they reached their ripe old age without diving. We have done some vacations together, and they kept talking about going to Australia with my wife and me. I told them that if we went to Australia together, we would have to dive the GBR, and they would have to get certified. California is too cold to get certified, they believed, and so they wanted to do it somewhere warm. This past fall, they flew to Colorado and did their pool work and academics with me, and then we flew to Akumal, Mexico to complete their OW certifications.
Here is roughly what those certification dives looked like. Each dive was in the neighborhood of 45-60 minutes. I won't mention the surface skills, which were not a part of the dive time, and I won't mention the ascent and descent skills that are part of normal diving. (I am doing this off the top of my head and might have the order a little mixed up.)
Dive One: No skills required--just enjoy a 45 minute dive.
Dive Two: While we were swimming around and enjoying the fish and coral, I had them recover regulators and clear masks. We also did two OOA drills. All that took only a small portion of dive time.
Dive Three: We went to a place with a mooring line and did the CESAs right away. While we were exploring the coral reef, I had each one do a compass direction and reciprocal. They had to clear their masks while they were swimming along as well. That dive was especially leisurely and took close to an hour.
Dive Four: Another leisurely dive lasted closer to an hour. Along the way, they had to remove and replace their masks while swimming.
Not so bad, was it? And they never touched the bottom, let alone kneel on it. We spent the rest of the week just diving together as friends. They even did two cenote dives because the cave guide who led them knew they were instructed in horizontal trim and would be better than the average beginning diver. They did great.
I am in Florida now. They flew out last week and we did their AOW certification in the warm waters here. They now have nearly 20 dives and are ready for Australia in April. I have dived the GBR before, and I expect conditions to be well within their skill range.
They are so enthused by their diving experiences that they are thinking California might not be too cold after all.