Ususally, people spear fish as a side benefit to scuba diving. I don't think I've ever heard of anyone learning how to dive just to spear some fish.
Save yourself some money and just buy your fish at the market.
Oh yeah, spear fishing is like any other kind of fishing. The more knowledge and experience you have, the better you will be at it. You can't "learn" how to spear fish over the net. You've gotta get wet and log some dives.
If you are still not discouraged yet, here's a short list of what you will need.
Boat & Motor - all the good fishing sites are not accessable by shore. If they are, they are either a Marine Sanctuary, or over-fished. Boats & Motors are not cheap.
Your basic scuba certification will cost you $100.
You can rent gear, but you'll want to buy your own if you're doing that many dives.
You're looking at about $3000-$5000 for a good set of gear, including drysuit. That's the low-end. A good drysuit will run you around $2000 alone. A good regulator is close to $1000. The costs on good scuba gear is staggering.
I say "good", in that most of us divers, usually want to come home after a dive. Why anyone trusts their lives to crappy scuba gear is way beyond me.
Anyways, I could go on and on, but I won't. If you're interested in scuba diving in the Pacific Northwest, feel free to check out my site, Diving The Northwest.
http://www.divingthenorthwest.com