Well first of all for spearing while scuba-ing that's very frowned upon... and i advise you to at least try the basic of free diving then start spearfishing.... Anyway the best shop for spearfishing gear (which is to one of my friends) is located in soug wakif and is very easy to find. check www stateofqatar dot com and you'll see the directions to reach the shop there. you can also see some of our clips and pix overthere.

Again just to remind you that spearfishing while scuba is very frowned upon. The team I dive with might scuba and spearfish occasionally but that's only in deep waters and extreme currents (talking about depths of 40m+) whereas most of our dives and spearfish are free-dive and remember 1 thing in spearfishing: ecologic hunting, that's shot the fish you are willing to eat only and spare those which are too small and might not have yet reached maturity.

i hope that was useful.