This excellent marine aquarium at the Waterfront Precinct gives you a close encounter with the denizens at the bottom of Darwin Harbour. Each small tank is a complete ecosystem, with only the occasional extra fish introduced as food for some of the predators, such as stonefish or the bizarre angler fish.
Also recommended here is the Coral Reef by Night , which consists of a tour of the aquarium, seafood dinner (on biodegradable plates, no less!) and an impressive show of fluorescing animals.