"[5] The bay’s coastline consists of a curved sandy beach of about 5 kilometres (3.1 mi) in length with a western end relatively sheltered from wave action by Point Ellen and an eastern end that is subject to "higher wave energy" with the result of "well-developed offshore bars" being formed and the Eleanor River being "constricted due to the large volumes of marine-sourced sand" being recycled and trapped in its mouth.

[7]: 370  Point Ellen is described as being "a grassy mound 8.5m high" that is "bordered by low rocks at its base" and is formed of a "Pleistocene aeolianite, i.e. a "dune limestone.

The Harriet River has an estuary coastal lagoon system at its mouth due to the local absence of the "bedrock cliffs" that dominate Kangaroo Island’s coastline.

[1][9][10][11] Vivonne Bay is recognised as having a significant undertow[12] and at times a sizeable swell, and is therefore suited only to experienced swimmers.

In April 2011, two Australian tourists drowned when a large wave swept them out to sea as they posed for a photograph with their backs to the water at Point Ellen at the western end of the bay.