Hi,
Two summers ago, we took a bus from the Seaworld parking lot to Bush Gardens in Tampa.
Sorry, I can't remember the bus company altho I think it was Mears. cost was $5. per person roundtrip which is cheap. We did have to pay for parking at SW which was $7. at the time.
I know if you post this question on the seaworld board, someone will have the name of the bus company and who to call.
herc.