Did a combined manatee snorkel, king spring dive with Pro. You snorkeled than returned to boat and geared up and swam over and dove the spring. You should probably call this a cavern dive. Basically go down to a big room. There were a lot of fish at the entry to the spring. Not so many inside. The water outside was greenish but the since the water flows out there the water inside was crystal clear.
We also snorkeled with manatees on Homassasas river. Saw more big ones there but it can vary.
Rainbow River can be snorkeled or dove. My wife just came along for the ride and stayed on the boat. Fun in that the water is so clear (think perfectly clear), that from the pontoon she could watch the divers which was fun for her. Some big bowfin in the river in a couple spots. Did rainbow with Pro. Rented a 3mm and it was a chilly day. Would go for a 5.
If you are flying in and out of Orlando, and you have some money left over, you might want to hit Epcot. Very popular dive in the aquarium. It is so large that I did not feel like I was in a tank, more like swimming down a flooded city street. Lots of fish and stuff in a tank. You do not have to even go into the park to do the dive.