I am also considering scuba diving...I have never snorkeled or scuba dived before...the more info the better...Thanks

Cocoa Beach,Satellite Beach they are good for snorkeling!

Don't even think about snorkeling in downtown Miami!
If you want to enjoy yourself, go down to Key Largo and take one of the MANY tours that are available there. Most are half day trips to the outer reefs of Pennecamp Park. If you have a car, downtown Miami to Key Largo , depending on traffic, is about an hour and a half.
For SCUBA, at minimum you will have to have to have several hours of instruction in a pool (they call this a resort course) before you will be permitted to go and then you will have to be with an instructor all the time.
Since you have never done either before, try snorkeling first. (I assume you can swim, otherwise learn to do that first).

Have fun!

In Key Largo check out the Christ of the Abyss statue near Pennycamp state park. The parrot fish and firecoral is amazing there. The Christ of the Abyss staue is a 50ft statue of Jesus donated to the state of Florida from Italy sumberged just off of Key Largo.