I learned scuba in a swimming pool with an excellent instructor. Being a bit timid, I would agree with Ted (OC Diver), that you want to do a lot of drills to make sure you have your act together -- like how to deal with your mask flooding. Good diving instruction includes all of those things. As a matter of practicality, having a lot of gear, tanks, compressors, etc aboard is a big hassle. I have never used the system, but for simplicity I would investigate the little pump devices that provide continuous air for shallow diving. You are tethered to your air source, but you need less equipment. Usually, the average boat captain just needs to go down a few feet and clean off a prop, or something of that nature. In any case, learning to dive by doing a lot in shallow clear water until you have the fundamentals down to the point where you do not need to think about them is the way to go.