Every year is different..... but we went last year and fully expected the place to be crowded, so went to do ICE! at Gaylord Palms in the morning, and decided on going to SW to do the shows, since crowds don't matter when you're not queuing for rides
To our complete surprise, the place was practically empty, and we were able to see the shows we wanted to see and hit the rides multiple times right up to park closing (Kraken in the dark = AWESOME).
I would say that in the morning it may well have been very busy (a lot of the staff were commenting on it and looked completely frazzled), and after lunch folks head off home having had their holiday weekend, leaving the park a very empty place.
As a side note, we chose to visit Aquatica on Thanksgiving itself, and found it to be even more deserted than SW. It was a gorgeous, unusually hot day, so we expected crowds and figured we'd just swing round if it was packed. We arrived at around midday, and were pleasantly surprised to be able to park in the row immediately next to the entrance pathway!
Hope this helps all who wanted to know!
Baz
