Most of the macroinfauna from sandy beaches is highly mobile, emerging out of the sediment when the tide rises, and using theswash to migrate up and down the beach face or feed (searching for prey or carrion). After swash excursions, they usuallyburrow back into the sediment, maintaining zonation at low tide. Therefore, the different species abilities to emerge, movearound and burrow under different swash climates and sediment conditions are expected to influence observed distributionpatterns. Nonetheless, few attempts have been made to understand behavioral mechanisms of these organisms in moving fluids.In this study, we used a flume tunnel to investigate the orientation, swimming ability and burrowing time of two similar species ofcirolanid isopods, Excirolana armata Dana and Excirolana braziliensis Richardson, under current velocities ranging from 5to 30 cm·s-1. E. armata inhabits middle levels of dissipative to intermediate beaches, while E. braziliensis is found towards theupper level of a wider range of beach states. Both species oriented countercurrent above a threshold velocity, which turned outto be significantly lower for E. armata than for E. braziliensis. E. armata proved to be a stronger swimmer as shown by thehigher velocities surmounted, and the less drags experienced at the highest current velocity. E. armata also burrowed fasterthan E. braziliensis. Burrowing time was affected by sediment grain size and water content, but not by water flow. Onceorganisms managed to begin burrowing under different flow conditions, they were not affected by current velocity.Nonsaturated sand precluded burial, while coarse sand retarded it. Differences in the observed patterns of across-beachdistribution may thus be the result of species-specific behavioral responses to swash climate, manifested in swimming ability,burying and orientation in directional flows.