There is a free shuttle between Sea World and Aquatica, and a free shuttle between Sea World and Discovery Cove. It is a little confusing where to wait for the shuttle as it is not clearly marked, and the shuttle for SW from Aquatica did not stop exactly at the appointed place anyway, he parked across in the lot and got out and shouted toward the curb, "anyone going to SW?" No shuttle directly from Aquatica to/from DC. But I hear it is also true that if you pay to park at one, you can park at the other free by showing your parking tag. Parking is always included or "free" at DC for paid visitors.