Perched high in the dunes of K'gari (Fraser Island), Lake McKenzie is a perched lake - rainwater held above the sea by a base of compacted sand and leaves - and one of the most beautiful bodies of fresh water in the country. Its sand is pure white silica, its water so clear and pure it is almost sterile, shading from white shallows to deep sapphire. Ringed by white beach and forest, it is the jewel of the world's largest sand island, reached by four-wheel-drive on the inland tracks. Swimming in its soft, clear water, fringed by blinding sand, is unforgettable.