Upvote:4
Couple of parts to this answer:
Specifically:
Dive shops are on the west coast of Bequiea, in Port Elizabeth; On the south west coast of St Vincent, at the Blue Lagoon, the west coast of Carriacou etc
They all have a good web presence, so as @uncovery mentioned, you can google for "Grenadines dive" or "Grenadines scuba"