[2]: 1, 2 Cook Island is formed of “rocks from the Lismore Basalt Group, formed by lava flows from the Mount Warning Shield Volcano approximately 20 million years ago.”[2]: 2  The Island is a “protrusion of eroded basalt” of a maximum height of 24.8 metres (81 ft) above sea level and topped with a plateau.

[2]: 2 Access to the island is considered to be not “easy” by the NSW National Parks and Wildlife Service because of the “exposed rocky nature” of the island's coastline and “frequently rough sea conditions.” Access is not promoted to “protect roosting birds and the nest burrows of wedge-tailed shearwaters which are fragile and can easily collapse under foot traffic.”[2]: 7, 8 As of 2011, there were twenty five native plant species which occupied, in part, three distinct habitats - “elevated locations; rocky crevices; and lower sites at the base of cliffs.”[2]: 5 As of 2011, vertebrate animals were represented by 25 species of birds and two reptile species.

[4] Cook then continued sailing north along the eastern coast of Australia and named two nearby landmarks, Mount Warning and Point Danger, after he was nearly shipwrecked there.

[3][7] Australian spearfisher Ben Cropp reported the sighting of a European vessel, wrecked on the island in the 16th century.

[8] In 2008, two fishermen, Joel Coombs and Malcolm Anable, were rescued from nearby the island, and later hospitalised, after they were thrown overboard as a result of their boat overturning.