Tidal outflow from Leschenault Estuary in winter forms an unsteady surface buoyant jet in Koombana Bay on each outgoing tide. As the water moves away from the exit channel and spreads radially over the bay, it assumes a plumelike nature. The mean features of this buoyant outflow, such as the plume shape, frontal celerity, internal circulation, and the bulk entrainment, were measured in an intensive field program. These features are shown to compare favorably with results from previous laboratory investigations and predictions from a simple inertia-buoyancy force balance which includes entrainment at the front. The stability of the plume frontal region was examined, and it is shown that subfronts were present, but their behavior cannot be explained by reference to previous work. ¿American Geophysical Union 1987