The Neptune Islands consist of two groups of islands located close to the entrance to Spencer Gulf in South Australia. They are well known as a venue for great white shark tourism. Description The Neptune Islands consists of two groups of islands, the North Neptune Islands and the South Neptune Islands. These both sit on the southern aspect of the Australasian continental shelf separated by a distance of . The North Neptune Islands which are south south-east from the mainland at Cape Catastrophe, consist of a large island of height and a small islet of height located from the main island's north-east point with a combined area of . The South Neptune Islands which are south-south-east from the mainland at Cape Catastrophe are more evenly portioned in height with the northern island being high and the southern island (also known as Lighthouse Island) rising to . The Southern group has an area of . A third feature associated with the overall island group is an outcrop of rocks known as Low Rocks located about north-north-east of the northern group of islands. Formation, geology and oceanography The Neptune Islands were formed between 10,800 and 12,000 years ago when sea levels rose at the start of the Holocene. The islands are remnant igneous inselbergs which have survived the erosive process associated with sea level rise. The remnant rock is described as being "a porphyritic granite gneiss and pink granite intruded with dolerite dykes". Remnants of the once-overlying calcarenite layers are also present on the upper platforms of the island. The soil is mainly derived from the weathering of the granite with a minor contribution from the weathering of calcarenite strata. The seabed falls steeply away from the coast of both island groups. Water depths of are reached within a distance of from the Northern group and within 1.5 km to from the Southern group. Flora and fauna Plants While the low profile of the islands do limit what can grow due to wind exposure and salt spray, surveys have shown that the Northern island group (excluding the "small satellite islet") has 35 plant species while the Southern group has 28 species on its north island while Lighthouse Island has 13 species. The latter is attributed to combination of the disturbance caused by activity associated with the formerly staffed lighthouse, airstrip, an introduced goat population that was eradicated in 1968, and burrows made