With regards to the safety, sure I appreciate it shouldn't be replied upon but I like to have the trigger set fairly sensitive so like to have the safety on to prevent premature discharge (so to speak). Also when swimming around with two mates and stalking in shallow water (where I do most of my spearing) it makes sense to have it on. ...
I agree with SubSub's post above, Safety Catches should not be relied on to provide safety. Slack bands (i.e. unloaded) is the only safe state. Also, once you miss a good fish because the safety is on or stuck, it soon looses its appeal.
I understand your concern though, I spear alone partly for that reason. I snorkeled with my son this Summer, which was great fun, but both felt we'd rather spear alone for fear of spearing each other. Indeed I encountered numerous other spearos this week - unusual - and felt that a couple of them were not sufficiently conscious of others around them nor the danger that they themselves presented to others. One was close to shore on a small, crowded beach, with a loaded speargun, in camo, with no dive float, two children next to him, a couple of others snorkelling close by, and "play" kayaks not far away. He also appeared to be distracted (not actively hunting). Not just for safety sake(but that is reason enough) but for public relations - we need to be safer than that. "Slack bands".
Much further out, I called out to another spearo to let him know I was nearby and told him that I would stay clear of him and move away from his area (which meant that I had to skip the first prime dive site I had planned to visit but
safety first). But he ignored that and followed me, tapped me on the shoulder just as I was lining up on a decent pollock that I had spotted, just within range, and as I was deciding whether to dive after it or shoot! We chatted but then he followed me and cut across my path before I finally shook him by leaving the safety of the bay. He seemed like a nice chap and I expect he felt it would be
safer for us to dive to together as buddies but, while I have some sympathy with that approach, it is not my chosen way to spearfish. I feel much
safer alone. I felt very unsafe near him and I felt that I presented a danger to him while we were close to each other. I did not want to be forever checking out where he was before taking a shot. Each to their own.