Simulations of tidal currents and salt transport in San Francisco bay are shown in these computer graphics animations. The "Tidal, Residual and Inter-tidal Mudflat" (TRIM) model is a depth-averaged tidal hydrodynamic model which solves the depth-averaged shallow-water equations. The governing equations are solved by a semi-implicit finite-difference method. The TRIM model was developed jointly by Ralph T. Cheng of the USGS and Vincenzo Casulli of Trento University, Trento, Italy. For technical details, consult the following references: Casulli, V. 1990, Semi-implicit Finite Difference Methods for the Two- Dimensional Shallow Water Equations, J. of Computational Physics, Vol. 86, No. 1, p. 56-74. Cheng, R.T., Casulli, V., and J. W. Gartner, 1993, Tidal, Residual, Intertidal Mudflat (TRIM) Model and its Applications to San Francisco Bay, Estuarine, Coastal and Shelf Science, Vol. 36, p. 235-280.