Hourly water level and current data were collected in Mississippi Sound and the adjacent continental shelf from April 1980 to October 1981. Amplitudes and epochs of the principal tidal constituents were calculated for each location. The data were used to construct cotidal charts and describe characteristics of the predominant diurnal tide. The pattern of the diurnal partial tides on the shelf is explained by reflection of first-class waves propagating normal to the coast. The period of the K₁ tide equals the inertial period just offshore of Mississippi Sound. The resulting diurnal shelf currents are Sverdrup waves with typical speeds of 5–10 cm s⁻¹. The tidal wave is transformed into a rectilinear shallow water wave as it enters the tidal inlets of Mississippi Sound. The form number of the shelf currents changes from 8·5 to 2·1 in the inlets due to enhancement of the semidiurnal currents. This is a result of continuity constraints, which transform currents in the inlets. Within Mississippi Sound, the tidal waves shoal and become increasingly progressive in response to bottom friction.