Hydrodynamic analysis and in-situ measurements of suspended sediment were conducted in the eastern South Sea to reveal the source and dispersal patter of the mud accumulating in Jinhae Bay, one of the largest bays in the region. At two anchor stations and three transect lines within the bay and at the entrances were obtained time series of suspended-sediment concentrations and current velocities for one or two tidal cycles. The results suggest that a slight net influx of suspended sediment occurs consistently during May, June, and August representing the sea conditions of predominant fair-weather climate. This study also shows an exclusive pathway of the suspended sediment through the southern entrance between Geoje and Gadeok islands. For the other northern entrance north of Gadeok island, although proximal to the Nakdong River, its contribution as a conduit of suspended sediment is negligible. The regional tidal patterns and landsat image of turbid plume around the Nakdong River mouth clearly indicate that the suspended sediment delivered from the Nakdong River is transported toward Jinhae Bay.