HR Wallingford was commissioned by The Rural Research Institute of the Korea Agricultural and Rural Infrastructure Corporation to carry out various studies relating to the final closure of the Saemangeum project offshore dikes currently under construction on the western coastline of South Korea. In addition to the numerical modelling of the complete closure works, reported separately, a schematised physical model of one of the closure gaps was constructed to investigate the flow regime during the final 100m of dike closure.