I can't imagine how it must hurt to be shot with a speargun. It not only hurts initially, but stays in you wobbling around until it can be carefully removed. Unlike real guns, almost all incidents involving people being shot with a speargun are accidents. The best way to avoid accidents is to be prepared.
Speargun safety has to be talked about amongst the divers. As with any gun, you never point it at anyone. When hooking up the rubbers, the spear is always pointing down and the safety is on (if you have one). It's often the homemade guns that have no safety. The quality commercial spearguns have very good safety mechanisms.
If you are snorkeling while you hunt it is easier to keep space between you and your friends. It's better to be hunting quietly alone if you hope to catch fish anyway. It's good to agree on which areas and direction you'll be going and have a plan to meet at a specific time and area.
If you are scuba diving you have a couple of different issues. If you separate too far you will no longer be a dive buddy capable of helping. If you are hunting together you run a larger risk of accidentally being struck by your fellow diver. You will have to talk about this before going down. You'll need a safe distance to hunt that is still close enough to assist a fellow diver. If possible have only one diver use a speargun and the buddy stays clear of the hunt but is always watching and is ready to assist in case of emergency.
I used spearguns my entire life without injuring myself or anyone else. It's something to be proud of because many people are struck every year. These poor folks aren't shooting themselves on purpose. These are accidents by people who look experienced and organized. This points out the danger in using these weapons to hunt. Mistakes are usually big ones.
I can't see us removing human error from our world so we'll just have to know that it exists. If you are a person that doesn't want to get shot while you're spearfishing with your friends then not only do you have to think about gun safety but you need to know your friends are as well. It's your best shot, but even that is no guarantee. Talk about it a lot. Show real pictures of people shot so everyone realizes their very important responsibility while using a speargun. Even after all is done for safety you will still need to talk about emergencies. It might seem like a real buzz kill to talk about emergencies before you go hunting but it could save one of your lives. I think it's worth a conversation and a plan of some sort.
I am into water safety. If you'd like to share information please go to http://www.adventure-ocean.com/blog.html
I am Christopher Bassler and I spent 40 years living on Guam. Guam is a part of the Marianas Islands. I am a Dive Master and had my 100 ton captain's license for 20 years. I was the Chairman of the Dive Safety Control Board at the University of Guam for several years. My field is water safety. Please visit my site http://www.adventure-ocean.com and help me spread the word and save lives through education.