I do a lot of speargun
fishing. The best advice I can give is to spend the
money to get a good gun. It doesn't have to be a high end one, but a
cheap gun will make you hate the sport, you will wound a lot of
fish without bringing them home and you will spend a lot of time working on the gun. Expect to spend $250-300 for a decent gun and extra spear.
As for brands, AB Biller, Riffe, Sportasub make good
guns, although there are many others too. Stay away from the low end JBL's and Buechats and any gun that looks cheaply made (they are obvious and numerous). I have an AB Biller and find it to be the best price/performance. Riffes cost more and are worth it.
You won't be happy with a short gun. I find 48" to be a good all-round reef gun and for open
water around
reefs. If you plan to
fish open
water predominately for pelagic and larger fish, get a larger gun.
A good gun will have a good, smooth trigger mechanism (Riffes are the best), stainless spring steel shafts and long barbs. Get a shaft or spear tip with a 3" barb. I prefer shafts without separate tips for higher performance, but exchangeable tips do give you a few options.
As for laws and
regulations, they differ widely from complete bans to specific seasons to completely open depending where you are. You will just need to do some
research on that. One thing I can't stress enough is NEVER break the law or go against
regulations. Everyone takes these laws very seriously - you would have a better chance escaping harsh fines and jail if you had a firearm outside the law instead of a speargun.
Good luck, spearfishing is a lot of fun and provides excellent dinners!
www.svreach.com/fish-2/
Mark
BTW, what does Tom Neale say about spearguns?