The spatial distributions of basic water parameters in the Puck Bay, a small semi-closed water body located on the southern coast of the Baltic Sea, were often typical of upwelling phenomenon. In such situations, like those observed in July of 1999, temperature decreased locally and water transparency increased locally. The present study analyzed conditions under which upwelling occurred using maps of horizontal currents at different depths, which were obtained from an operational hydrodynamic model. With north, northwest winds the upwelling in Puck Bay looked like the shallow-water upwelling arising as a direct dynamic response of the water body to the wind direction, without a distinct effect of the Coriolis force. However, upwelling water circulation during other wind directions, i.e. west and northeast winds, did not match this simple scheme and was affected by coastline configuration. The results of many years’ measurements pointed at an important role of upwelling in hydrological regime formation in the shallow parts of the Puck Bay.