The influence of coastal structures on coast's water quality is the subject of the present paper. Water exchange in the space between groins due to breaking wave induced currents is studied by experiments, numerical and hydraulic modelling. The results give the possibility to estimate the water quality for the area of the coastal zone, enclosed by the shoreline and the pair of shore-normal groins. That may be considered as an example of estimation of the effect of typical shore structures on the water quality.