The oceans and seas under Australian jurisdiction include the full range of ocean temperature zones, from tropical to polar, ranging from the spectacular coral reefs of the tropical north to the majestic kelp forests of the temperate south. This environmental diversity explains the rich variety of life found in Australia’s oceans. Australia's marine environments contain more than 4,000 fish varieties and tens of thousands of species of invertebrates, plants and micro-organisms. Large areas have been little explored and new species are often discovered. Scientists estimate that about 80% of the species in Australia’s southern oceans occur nowhere else in the world. This paper looks at competing uses of the oceans, threats and regulatory arrangements.