My view as a non spear hunter. I understand the dynamics of this & our shops have Pole spears, Hawaiian slings & different types of guns, band, air psi etc. I go after game with my D500 camera instead. That said I am sure that if I were hungry for fish or other critters, & I do like fresh tuna, I could operate these. All these devices are made for one thing, to kill, & like a gun should be respected similarly. When entering or exiting the water they should be made safe, unhook bands, covering the barbs, handing it with the business end pointed in a safe direction. I have been diving with others that use them and there are two thoughts here. Dive with them as a buddy or dive in another location previously agreed to ensuring you don’t accidentally strike a diver out of visibility range. Some places manage game, size, qty, etc. take or prohibit it. Ensure where you take game allows this or it could costing you a lot more than you expect. My $.02 worth Dalelynn