[1] Michaelmas Island has steep rocky shores with submerged reefs all along its northern southern and eastern sides in depths up to 30 metres (100 ft) with large granite boulders.

The faces are covered in a diverse range in corals and sponges and home to a wide variety of marine life.

A whale chaser “Cheynes III” that was scuttled in 1982 is located off the western side of the island and is regarded highly as a diving site.

The habitat of these species is threatened by weed invasion such as Taylorina and feral animals such as rats.

[5][6] In 2016 the island was chosen as a new habitat site for the critically endangered Gilbert's Potoroo.