Aquascene is a very Darwin sort of attraction: informal, tidal, and built around wildlife that comes and goes on its own schedule. At high tide, schools of wild fish move into the shallow water at Doctors Gully, where visitors can feed them by hand under staff supervision.
It is simple rather than spectacular, but that simplicity is part of the charm. Check the tide-linked opening times before heading over, and treat it as a short family-friendly stop near the city rather than a full afternoon plan.