Hi Ben,
A lot of interesting comments on this thread. Here's some info.
In W.A. you can use SCUBA and a spear gun, but don't expect to make any friends in spearfishing clubs, we all freedive and won't dive with a bubbly. It's not considered sporting. Most freedivers have a SCUBA ticket, but don't use it unless retrieving stuck anchors in deep water etc.
We generally dive for 4-8 hours a day on weekends or good days. You can't do that with a tank. You may be able to whack a Baldy or some other dumb (and tasty) fish, but anything sporting that is a bit cluey or flighty and the bubbles and all the racket made by the reg scares them off.
Forget a woody, no serious spearo uses them, same with pneumatic guns. Every diver in our club and the other main spearo club in Perth use rubber powered rail guns, there are good reasons for this.
You may think you can only dive to 4 or 5 metres on a breath hold and stay down for 20 seconds or so, but with correct training, practice and fitness, 20m is easy and 1-1.30 min is a standard decent dive. Some of our club members can do more than 2 or 3 minutes and can dive to over 30m.
My advice is to join a club before you buy anything. Ask the members what gear you should look for. They will often know cheap places to get it, or may have discounts for their club with some of the local retailers, and often sell their surplus used gear cheaply. They will take you out on a boat and teach you to dive properly, safely and how to hunt fish.
I started with a 1.0m Rail gun and a set of Picasso Black Team plastic fins and a surfing wetty. They did me to begin with, but I could have saved much money and time by joining the club earlier. I couldn't dive below 3 metres due to ear clearing issues and lack of mental fitness. I now dive with a 1.4M rail gun, glass composite long fins, freedive suit and other more "appropriate" gear, have no problems at up to 20m and have a good breath hold and no clearing issues and it didn't take long (this aint blowing my bugle as it's considered very average in dive circles).
Contact Bluewater Freedivers of WA
www.bluewaterfreediversofwa.com/ and come to the next meeting (3rd Tuesday of every month). You're welcome to come along with me if you like.
There are a couple of good forums too. Try Spearoz, Deeper Blue, spearfishing.com.au (just google the names)
Leave your tanks behind and experience the deeper blue naturally.
Cheers,
KH