Results are presented from a series of experiments investigating the internal and near-bed dynamics of restricted net exchange flows across a submerged sill obstruction. Experimental measurements focused on obtaining high-resolution velocity and density profiles in the vicinity of the obstruction to observe and quantify both interfacial mixing and boundary layer processes under a range of parametric forcing conditions (i.e. variable saline and fresh water flow rates; density differences; water levels). Detailed synoptic velocity fields were also measured across the obstruction through particle image velocimetry (PIV) to aid qualitative and quantitative interpretation of these internal and near-bed flow processes, with a focus on defining the specific parametric conditions under which saline intrusions could become arrested through erosion of the intrusion nose at the bed boundary by the freshwater outflow layer. In this regard, it is anticipated that the study findings will provide an important step towards achieving improved representation of interfacial mixing and boundary layer processes within semi-enclosed estuaries and fjords, which are often poorly represented in current numerical models.