The hydrodynamics of coral reefs control the transport and availability of sediments, nutrients, coral larvae and consequently, all life across coral reef systems and across all spatial and temporal scales. In this study, we investigate the hydrodynamics of a distinctive feature of forereef morphology known as spurs and grooves (SaG). Despite their presence across coral forereefs, there is limited in-situ hydrodynamic data of SaG, and no current data reported from the Great Barrier Reef (GBR). Here, we analyse a hydrodynamic dataset obtained in prevailing weather conditions with low wave energy over SaG at One Tree Island in the southern GBR, a platform reef with a large lagoon isolated from the open ocean during low tides. Our data show that, for the conditions measured, flow velocities in forereef SaG are controlled by tidal water levels, with greater flow velocities observed during low tides. Throughout the full tidal cycle, offshore flow occurs at the upper forereef groove, indicative of lagoonal outflow. Further investigation into the influence of these hydrodynamic conditions can assist in assessments of forereef morphological evolution.