Australian offshore jurisdiction is among the most complex in the world, not least in part because of the division in jurisdiction between the Commonwealth Government in Canberra, and the Australian state governments. State jurisdiction is increasingly important in Australia, with increases in maritime capabilities for state police forces, the proliferation of state marine parks as part of the suite of national parks and the relevance of state jurisdiction to native title. This article provides an introduction to the determination of maritime jurisdiction vested in the Australian states, an area of law generally poorly understood and seldom considered by publicists.