In the early to mid 90's, if you bought a 5 day park hopper (about $135), you got unlimited admission to Discovery Island, River Country (a closed waterpark), and Typhoon Lagoon for 7 days from your first theme park use.
We would get the tickets which did not expire and go to the theme parks a couple days and spend the rest at those 3 parks.
Discovery Island was small--you could tour the whole thing in a couple hours. It had naturalists like at Conservation Station that held a bird or reptile and let the kids touch it. I think it was between Fort Wilderness and the Contemporary.