[spaghetti]

I agree with Oldsarge on the ethics thing. Until you have one single shot in a breathold it's a loyal duel with the fish, no matter how sofisticated the gun is. (Is a good speargun less ethic than a crap speargun? No).
The technical issue will be probably the aiming line. Tbgsub made a very fine job on his Cobra, but the lazer source is mounted under the barrel, so its projection is not on the same axis of the spear. This way I think the lazer dot does not tell you exactly where to aim...