The specific form of permeable groins, consisting of wooden pile rows, have been used for coast protection. However, the hydraulic functioning of such structures has not been understood well. As the pile groins become older and the maintenance costs increase, the issue of their effectiveness has become of importance, while no serious research has been undertaken. This study tries to tackle this issue. Based on experimental data (Hulsbergen and Horst, 1973), the functioning of pile groins has been revisited by an advanced numerical model. The simulations give deeper insights into the effectiveness of permeable pile groins under well-controlled laboratory conditions.