In this paper, an initial hydrodynamic model for the Mississippi Sound is presented. The paper presents the conceptualization of the problem, the computational mesh and boundary conditions, results of on-going model calibration, and a computational experiment for estimating Lake Pontchartrain flushing time. In addition, existing observed data on nutrients, salinity, suspended solids, and chlorophyll-a are presented to support the framework on which a future water quality model will be developed.