Hi Diver!
My name is Ivan, I am cape Verdean originally from Santiago, lived in Sal in Boa Vista for more then 10 years, about spearfishing I can give you some info. I don't know what do you mean ( Praia as an Island or City itself, if you mean Santiago Island I recommend you to go to Tarrafal the locals are very friendly and helpful and they love spearfishing, and fishing in general.
I am living in Belgium at moment...
But In praia its no very familiar that sport.
I hope it help... Ivan