[PhilLJCA]

you can make a laser sight for a speargun easy enough. just buy a bb gun laser sight (daisy makes one thats more than good enough for speargun range) and enclose it an a miniature o-ring sealed glass tube (similar to the housing unit for underwater cameras). if you have a pneumatic gun you can attach it to the top of your gun, if your gun is band powered then you will either have to mount it on the very front of the gun (tricky), on the side(s), on the trigger mech, or come up with something very creative. either way, i would view it more as a training tool than as a permanent hunting device...but who knows. let us know how it turns out.