Silver Springs is one of Florida's classic natural attractions: a huge clear spring basin feeding the Silver River through subtropical forest. The glass-bottom boats are the old-school experience, and still a good one, because the water is clear enough to see fish, turtles, spring vents, and submerged vegetation below the boat.
For a slower visit, rent a kayak or canoe and paddle the river. The banks are thick with cypress, palms, and live oaks, and wildlife sightings are common. It is the one Ocala sight that can justify the detour on its own.