No one mentioned swimming. Can you actually swim without gear? Can you swim comfortably for a mile? How about under water holding your breath? Can you do fifty meters, that's length of Olympic size pool?
I don't mean to insult but you asked. But my "basic" open water training included lotsa swimming and underwater swimming (one breath). We also played underwater rugby, or were required to thread water for 15 minutes with both elbows above water (running helps with that).
I admit, I am not in condition to do anymore that, except for swimming, but than again I was out of diving for 30 years and I'm just getting back into it. That's my goal and I offer you this challenge to consider.
I'm sorry but I'm an old CMAS guy, and when I started diving in 1990 (14y old) the course consisted of pool training for the better part of a year... starting in september and if you were lucky you would do your first openwater dive in april. Most of the pool training would consist of swimming, apnea (both underwater swimming, static, and while doing "tricks"), breathing from tanks without regulator, sharing a tank and breathing off it with 7 people, etc etc etc. This then forwards to dive training asking to do free diving emergency ascends from 40 m (120ft), emergency rescues from 40m (120ft) not using the BCD (so swimming up), etc. I know, I did all of that.
All under the assumption that you need to be fit (YES), need to have some feeling for being in the water (YES but just a modicum)and that you need to be a navy seal (NO).
Some of the absolute worst divers I have EVER met, come from this school of thought. Yes they are good swimmers, Yes they can hold their breath for 3 minutes straight, and they feel on top of the world. But their gun ho attitude, show no mercy, we need to "attack this dive" kind of EGO driven dribble has caused more underwater incidents than you can imagine. Yes my opinion is quite strong on this one as you can probably sense
SCUBA DIVING IS NOT SWIMMING! Yes your aerobic capacity will increase but you can just as well do long runs, take your bicycle out or do any other strenuous activity to accomplish that.$
In the end what makes you a good diver IMO =
- good basic underwater skills (and these are not so easy as most believe)
- good awareness both above and underwater
- Varied experience (not all your dives in one local area)
- the ability to assess and reassess your own skills and experience, and a keep learning mentality.