Inner Middle Ground Nine Foot Shoal is a compound, parabolic, inlet-associated shoal in the entrance to Chesapeake Bay. The bathymetric development, sedimentologic make-up, and hydrodynamic environment of this dynamic feature indicates that it is in quasi-equilibrium with the ambient currents. Bathymetric comparisons among six surveys taken during the past 127 years trace development of the shoal from two linear sediment bodies to its present double parabolic morphology. Principal components and cluster analysis procedures were employed to categorize 75 surface sediment samples of the shoal into natural groupings. Large linear correlations were found between the weight percentages in any two adjacent size fractions when compared over the entire data set. As a result of this redundancy, the first three principal components accounted for more than 90% of the total variance in the original grain size distribution data set. These three components were solely used in the clustering procedure without a priori knowledge or selection of arbitrary limits to group the sediments. The four-group classification chosen for detailed review in this paper was reached each of the eight times the procedure was followed from different randomly generated starting partitions. The particle size distributions of the surface sediments were found to be systematically related to shoal morphology and to be in adjustment with the ambient currents. The tidal currents of the area were found to be of sufficient velocity to easily erode the surface sediments. Information from eight current meter stations on and adjacent to the shoal was used to investigate various flow asymmetries. Bathymetric influence on the flow direction of near-bottom currents is illustrated by diverted currents and shielding. Pseudosynoptic vertical profiles were used to estimate boundary shear stress, fluid power, and sediment transport. The indicated sediment circulation cell which maintains the shoal is a manifestation of the mutual evasion of ebb and flood tidal currents.