Are you at total new comer to scuba? If yes, try going out to Coki beach in St Thomas.
There is a beach concession there that is used by many of the ship excursions for first time scuba , but you can go there on your own. They will put you in the water and teach you the basics and then take you out to the reef in fairly shallow water and hold your hand through a first dive. I have no idea of the cost. All you need to do as far as I know is show up and say your ready to go. There is a dive shop near the beach entrance, I presume the guys on the beach are associated with them.
Coki is also a great beach , with facilities and is located next to the paid attraction called Coral World.