Wave-induced beach groundwater flow has been linked to sediment transport in the near-shore zone and chemical transfer from the aquifer to the ocean. The flow dynamics, however, are not well-understood. This paper presents a numerical study of the instantaneous (i.e., phase- resolved) wave motion and resulting groundwater responses in the beach zone. Simulations conducted for a representative beach reveal various important features of the flow. In particular, periodic local groundwater circulation occurs below progressive bores while the averaged flow behaviour is characterised by continuous circulation (due to wave set-up) extending from the upper part of the beach to the lower part. These results are analysed and compared with previous analytical solutions derived for simplified situations. The findings will assist future studies to quantify the effects of beach groundwater flow on other coastal processes.