GB,
You may be thinking of Clearwater FL. It's not on the Panhandle though. There is a lota diving in the freshwater springs there. Cool diving with the manities. The beach is a bit of a drive to get to though.
You are right about the Keys. Lotsa' of drinking and watersports, but if you do a search there is a lot of other stuff to do there. Skydiving, wildlife bird center, bowling, movies, High School football games, There are (2) beaches (Anns & Bahia Honda), tons of places to eat, more bars than you can shake a stick at, airboat rides not far from Florida City, lots of fishing, snorkeling, glass bottom boats, casino boat, ultra-lite rides, camping, kayaking............................ you have to look to find it all, but it's there. I used to manage the Pilot House Marina in Key Largo years ago.
I would recommend Ocean Divers in Key Largo. I used to take my dive classes there for their Open Water dives on occasion.