Numerical models may represent a useful tool to estimate wave overtopping discharge. However, so far there is still little available literature on numerical modeling, especially on Boussinesq modeling. The paper analyses the ability of a BTM, Celeris, to predict wave overtopping at a vertical seawall with shallow foreshore, comparing numerical outcomes with physical results of an experimental campaign carried out at the University of Naples Federico II, Italy. The validation has shown that the model needs to be calibrated to avoid overestimation and obtain a reliable tool. In this paper we opted to calibrate the Manning coefficient, which acts as an additional dissipative term to limit overestimation and achieve accurate assessments.