We report the current fluctuations in Lake Nakaumi, an enclosed brackish water body with a two-layered structure in western Japan. The study is based on the data derived from velocity measurements made by a method employing a current drogue placed in water and following it on a ship. In spite of a few exceptions that occurred under certain geographical or hydraulic conditions, the following inferences were made from the study: (1) remarkable changes in the surface current occurred with fluctuations in the sea wind, (2) surface water flowed in the direction of wind at a speed of c. 2% of the sea wind velocity, (3) the bottom currents moved clockwise under the influence of the tidal changes, and (4) the velocities of the bottom currents ranged between 3.9 and 5.3 cm/s.