The Great Barrier Reef’s Keswick Island is on the market for 30 million Australian dollars (about $22.5 million). A family friend of the British royal family is reportedly selling the island, which is 517 hectares (of which 400 hectares is national park) and can accommodate 1,000 dwellings and 3,000 people. The island has a sealed airstrip, water and fuel storage, and a dry marina. The island comes with a 117-hectare development lease from the Queensland government until 2096 and a 25-hectare seabed lease for a 180-berth marina to park your yacht, and deep water jetty.
Source: Lonely Planet