Simple budgets may be used to estimate the exchange of water in embayments that capitalize on the concept of steady state and conservation principals. This is especially true for bays that experience a significant exchange of freshwater. This exchange of freshwater may reduce the average salt concentration in the bay compared to seawater if it involves addition of freshwater from rivers, R, and/or precipitation, P. Alternatively, it may increase the average salt concentration in the bay compared to seawater if there is relatively little river input and high evaporation, E. Since freshwater input changes the salt concentration in the bay, and salt is a conservative material, it is possible to combine two steady state budgets for a bay, one for salt and one for water, to solve for the magnitude of the water flows that enter and exit the bay mouth. Students will make actual calculations for the inflow and outflow of water to Puget Sound, Washington and the Mediterranean Sea and compare them to actual measured values.