I think it was the Portugese, who followed on from the Senghalese and of course Indians from the Mauria Empire of Ashoka the Great, circa. 230 BC., the Chinese, sometime around 1st-2nd century AD, along with Roman traders camped out in Arnhem Land Gulf of Carpenteria way, as did the Phoenicians who left a sizeable colony there France and Spain got there after the Potugese and the Dutch, followed last by Britain.
"The theory of Portuguese discovery of Australia claims that early Portuguese navigators were the first Europeans to sight Australia between 1521 and 1524, well before the arrival of Dutch navigator Willem Janszoon in 1606 on board the Duyfken who is generally considered to be the discoverer. This is based on the following elements:[1][2]
The Dieppe maps, a group of 16th-century French world maps, which depict a large landmass between Indonesia and Antarctica. Labelled as Java la Grande, this land mass carries French, Portuguese, and Gallicized Portuguese placenames, and has been interpreted by some as corresponding to Australia's northwestern and eastern coasts.
The presence of Portuguese colonies in Southeast Asia from the early 16th century, particularly Portuguese Timor – approximately 650 kilometres from the Australian coast – c. 1513–1516.[3][4]
Various antiquities found on Australian coastlines, claimed to be relics of early Portuguese voyages to Australia.
Precedence of discovery has also been claimed for China,[5] France,[6] Spain,[7] India,[8] and even Phoenicia.[9]"
Theory of the Portuguese discovery of Australia - Wikipedia, the free encyclopedia