A simple model of open coastal dynamics is adapted to provide an analytic solution of the vertical and axial structure of tidal currents in an estuary. Applied to the Hey River estuary in northern Queensland, the model provides an accurate representation of the four major tidal constituents. By best-fit analysis of the model results to data from three current meters, the vertical eddy viscosity for the estuary is estimated as 2.8 × 10−3 m2s−1, and the linear friction coefficient as 8 × 10−4 ms−1. Bottom boundary considerations indicate that the data are consistent with the concept of a bottom logarithmic layer 0.6 m deep, in which the eddy viscosity increases linearly from near-zero to its free-stream value.