Mako,
Most of the spearfishermen I know predominately do it freediving and save the scuba for photography, salvage, and other purposes. Scuba is good for spearfishng the offshore wrecks off New York, New Jersey, Virginia and Maryland, though, where the water is colder and the visibility is less than further south.
You really don't need scuba to spearfish and you may find it detracts from the sport once you develop as a freediver. Freediving helps your scuba skills immensely and does not require a certification, plus it's a LOT more economical. I know lots of guys who can hunt freediving as deep as most recreational scuba divers will ever go (in clear water), but the fact is you really don't need to go deeper than about 30' max to spearfish most of the time. I know a local spot whre you can get plenty of fish in 10 feet of water or less. I primarily freedive/spearfish and seldom put on a tank any more, but I used to do a whole lot of scuba diving. I keep things more simple now and like not having to deal with so much heavy gear.
Having said all that, I've been scuba diving since 1967. It's a great sport. We have some of the best wreck diving in the world off the east coast. By all means get scuba certified. Go NAUI, stay away from divers with patches all over their jackets, dive with the guys using the most well-used gear, and always dive safe.
Mark