Hi I think you're thinking about Mistify. It's a fireworks/waterworks show which ends the day. It happens across the huge lagoon and I believe you cna see it best from the Atlantic bayside stadium or across at the Spice mill cafe.
Basically they have water funtains squirting up water, fireworks, soundtrack and they shoot up loads of water to form a dome then project a show basically about a little boy dreaming about his day at seaworld.
Is this the show you mean??
It's only on at high season, however I think it's when the park is open till 10pm. When we were there it wasn't on the first day we went Sat 28th March, but was the second and third visits when you got into Spring Break.
So I don't know but I'd take a guess that it probably wont be one when you go sorry - hopefully someone who's been in October can clarify