[en] A key feature of breaking bores, jumps, and spilling breakers is the roller region, characterised by intense shear and recirculation, associated with air bubble entrainment and splashing. Detailed unsteady air–water flow measurements were conducted in a breaking bore propagating in a large-size channel, using an array of dual-tip phase-detection probes and an ultra-high-speed video camera. The results showed a steep roller front, with a very-dynamic air–water bubbly region, albeit with a relatively limited air–water roller region. In this study, a major challenge was the inconsistency in light intensity linked to the travelling nature of the bore. A simple flow visualisation technique was applied to retrieve the two-dimensional side-looking profile of the roller edge and average void fraction. The results were validated independently with a phase-detection probe. While the probe data lacked spatial variability, the study reinforces the needs of high-quality validation data set, including in unsteady transient flows.