Sitting on the shore platform at Ben Buckler, the north‐east headland of Bondi Beach, Sydney, is a large isolated boulder, weighing around 235 tons. In this article I analyse geomorphological explanations for, and historical representations of, the boulder, locally known as the Big Rock. Explanations for and representations of Bondi's Big Rock typically appear in discussions and debates about changes to the New South Wales coast and the impact of storm waves and tsunami. Geomorphologists date the Big Rock from a storm in July 1912 and have identified a range of wave sizes and forms to explain its presence. Yet, neither their explanations nor evidence have convinced a number of local residents who claim the rock existed before the 1912 storm. Bondi's Big Rock is thus a valuable reminder that geomorphological features are not fully formed subjects. Rather, they must be defined and contextualised in inordinately complex processes of explanation and representation that ultimately are always interpretations.