I didn't start snorkeling until we started the 7 day so I cannot speak to the Bahamas. However, I can tell you that if you snorkel at Serenity Bay at CCay you should see more fish than at the family beach. It still won't be much, and you won't see much more than the white/silver and yellow guys but you may see more if you go out to where the rocks/reef is.
You'll just have to break down and go on the 7 day. The fish on the Barrier Reef on the Captain Marvin's 1/2 day snorkeling is way cool! Lots of colors to see out there. I'm still learning and am still gun-shy but it's an awesome experience, no matter what you see.
Have fun,
Kim