Garden Island is a narrow island about 10 kilometres long and 1.5 kilometres wide, lying about 5 kilometres off the Western Australian coast, to which it is linked by an artificial causeway and bridge.
Like Rottnest Island and Carnac Island, it is a limestone outcrop covered by a thin layer of sand accumulated during an era of lowered sea levels. The Noongar peoples tell of walking to these islands in their Dreamtime.
At the end of the last glacial period, the sea level rose, cutting the island off from the mainland. For the last seven thousand years, the island has existed in relative isolation.
Wikipedia https://en.wikipedia.org/wiki/Garden_Island_(Western_Australia)
Coordinates -32°12'7.379" N 115°40'38.121" E