Lady Julia Percy Island, known as Deen Maar or Dhinmar in the Gunditjmara language, lies 8.1 kilometres (5.0 mi) off the coast, in the Barwon South West region of Victoria, Australia in Bass Strait.

Deen Maar was well known to the Gunditjmara people; they believed that the spirits of the dead were conveyed across the sea to the island from a cave called Tarnwirring ("the flowing of the wind") at the top of a rocky sea cliff,[2] It is also the place where ancestral creator being Bunjil was said to have left this world,[3] and other spirits continue to fly over to Deen Maar before ascending to the stars.

[9] Also in 1802, Nicolas Baudin sailed past in his ship the Géographe, and recorded the island as Ile aux Alouettes,[9] a name that has not persisted.

[2] In January 1936 a scientific expedition from Melbourne University's McCoy Society visited the island for six weeks and carried out a comprehensive ecological survey.

[14] In the waters on the western side of Lady Julia Percy Island lie pieces of an RAAF Avro Anson aircraft.

The top cover of the fuel tank bay had the number AW-878 in pencil on the underneath side and the Mae West was identified as having been drawn and signed for by Flight Sergeant MacLellan on 15 February 1944.

[citation needed] Formed some seven million years ago, the island is much older than other volcanoes in the region, and is also unusual in being built by both submarine and terrestrial eruptions.

With regard to the flora, Frederic Wood Jones said in 1936 of the island, following his leadership of the 1936 McCoy Society expedition:[14]A century ago it was covered with a dense, almost impenetrable, growth of the mixed bushy scrub that characterizes certain parts of the coast of the adjacent mainland.

Some sixty years ago this dense scrub was still standing over the major portion of the island; but to-day the whole of the plateau is devoid of any growth more majestic than bracken fern and thistles.

These include some that inhabit the island permanently, such as the short-tailed shearwater, fairy prion, and common diving petrel, and also birds that visit from afar, such as the albatross, sooty oystercatcher,[17] and crested tern.

[15][1] Ground-dwelling birds include the stubble quail, swamp harrier, peregrine falcon, nankeen kestrel, white-fronted chat, Richard's pipit, welcome swallow, and little grassbird.

[17] Boat cruises from Port Fairy to the waters around the island are available; they allow people to see the seal colony and watch whales and seabirds on the way.