I used to do a LOT of spring spearfishing in the local lakes when in my early 20's. I used a little pneumatic speargun with no problems. (used the same speargun in the caribean with great success, too) You could only shoot about 4' with it underwater.
Best I found was a wetsuit with weightbelt to compensate; and a horsecollar bc. When I wanted a rest I could just blow a little air into the bc and lounge on the surface.
Make sure you have a good cord between the gun and spear. On larger fish I found a shot just behind the gillplate hoping for the backbone worked best, but immediately (during the second or two of "shock") try to grab the spear both sides of the head and take it up to the surface. If you do that they're manageable. Miss that window of opportunity and things can get, "sporty".
Back in the day I thought of trying for a record and had been continually seeking larger fish................. Let's just say there's a point where it starts getting a little too, "sporty", and instead I hunted for fun and fillet's.
Shallow weedbeds (3-7' deep water) have "fishtrails" all through them. These are a great spot for smaller fish like perch at intersections but you've gotta be quick.
As others have said read your regs, I know it's changed a lot here since I spearfished.
If it interests you, you should persue it. I had a lot of fun for a lot of years, and in the early spring even the irrigation lakes out here were almost caribean clear.
Best of luck with it.