[sancarlos]

Thanks, WetKiwi. Sometimes human curiosity makes us do stuff, which is not practical. Like hunting fish instead of going for it to the store, which is faster and cheaper (especially considering price of my Wong!). Or actually going places instead of watching them on TV.
And what somebody might feel as cheating I might consider as efficiency.
I guess every means to make the hunting more efficient (in terms of fish escaped after being shoot) is a good thing. And as long as people don't kill more fish then they need for dinner it is fine IMO.
I'm totally agree with Pastor that practice makes perfect, but I don't have access to any pool where I can practice, hence the solution of using laser. My son found it very helpful on his JBL, I guess I need more power and better mounting gismo for the longer-range Wong.
Murky water observation: actually the more particles are in the water the more convenient it is to aim since you see whole beam, not only dot on the target (as in crystal-clear water).
Price\size observation: DPSS module from z-bolt with 30 mw output (6 time the power I used) is only 129 USD, 55 mm long and 10 mm in diameter (no batteries). Not too bad sizewise and moneywise. The question is how to make it water proof and adjustable for each spear gun.

Aiming observation (a joke): PASTOR are you suggesting to practice intercontinental missiles more often to get a better hit rate instead of using technology?

Thanks everybody for your input and support.