Hi Tracy!
Welcome to ST and the most excellent world of diving!!! While you are searching for a dive op, I would recommend that you go on a smaller boat. They usually hold about 6 divers. They are typically more expensive, but it might suite you better being a newbie. Be sure to tell the company when you are booking and then tell the DM again when you get there that this is your first dive. The only dive op I've ever used in Coz is
Blue XT Sea They only have small boats and a great staff. There are many others and you will get tons of referrals here. Take your time and read everything on their websites. Have fun!!!