I haven't been to one of those "sea world" thing... is it a good way to spend time or is it a waste of time? I've been to the reptile park north of Sydney and it was quite a good experience.
Depends on whether you like fish ! I think it is interesting - especially since you don't usually get to see fish and other marine animals, especially some of the more exotic ones. Underwater World up on the Sunshine Coast is good, Sea World on the Gold Coast was okay - but they are more of a theme park, and the Sydney Aquarium is worth a visit too.