A 2-D RANS-VOF model has been employed to investigate the wave shape changes over low-crest breakwaters under regular waves. Our analysis demonstrate that wave skewness increases on the incident side, and then decreases to the minimum magnitude on the seaward slope of LCBs, it then increases above the crown crest and leeward slope to attain a maximum magnitude around the toe of structural leeward slope, and finally it decreases as wave propagating on the transmission side. Wave asymmetry decreases gradually from around zero values to negative values on the incident side, attains a maximum magnitude on the crest of LCBs, and then dramatically increases from negative values to positive values on the transmission side. We found that wave asymmetries increase with increasing wave heights and wave period; effects of water depths on wave shape changes can be ignored; the crest width of breakwaters influences the rate of increase of wave skewness above the crest and the leeward slope and affects the location of maximum magnitude of wave asymmetry. Calculated surface elevations and wave asymmetries are in good agreement with laboratory measurements collected in the small scale wave channel tests at the University of Cantabria (UCA).