if you have children who have see/enjoyed the movie Dolphin Tale, the real Winter the Dolphin is at the Clearwater Marine Aquarium. seewinter.com
I've seen some reviews and such on TripAdvisor, but have yet to make it there myself. i believe they offer a few different packages, mostly inexpensive, and offer a variety of things to do. Doesnt sound like a FULL day like trip, but worth a visit for a couple hours perhaps?