That is one seriously broad question that depends on how wishy washy you want the PoD to be and how the settlement starts. There are a pile of PoDs ranging from the theory of the Portuguese discovery of Australia in 1523, to Torres sighting Australia in 1605 or simply perhaps knowledge of the Torres Strait becoming known to the Dutch after that date. The Dutch then take over as explorers from 1606 to 1644 with Janzoon, Thissjen and Tasman at which point Dampier's voyage in the Roebuck could be the one under different circumstances given his commission was to discover Australia.
Any of these exploration PoDs could spear history off in very different directions.
Map from 1659