Spearfishing is an addictive sport/activity. I'd been a lino, like yourself, for years. But now, I'd much rather go Spearfishing.
If you're going to get a gun, I'd suggest you buy something decent. Just read the start of this thread, and you'll see what I'm talking about.
I've been Spearing for almost a year now, and my gun hasn't missed a beat.
You'll also need a few other things too:
Dive knife - To kill the fish once speared (More humane to kill a fish quickly).
Float with flag and float line - The float line is a 10-20m length of Nylon rope which attaches to the gun handle at one end, and the float at the other. The float is usually a fluro orange footy sized float, with a blue/white "Diver in area" warning flag for boaters and other marine craft.
Because the gun attaches to the float, you dont have to worry if you accidentely drop your gun. Just find your float, and your gun will be at the other end.
Wetsuit - Helps to keep you warm, especially in winter. You'll even need to wear one in Summer for dives longer than a few hours. Besides you wont have to wear sunscreen in a wettie.
I've bought heaps from here:
http://www.legendary.com.au/index.php
Learn as much as you can, and enjoy.
Joel, if your listening, I've just finished making my first "Custom" Float line. Clear PVC tube, Dyneema inner, and Stainless fittings at both ends. It came out a treat. Haven't tried it yet, but I'll let you know how it performs. Where are the pics of your trip???
Cheers, Shorerider.