Pollutants tends to accumulate in enclosed ponds, lakes, estuaries because the water stays in one place for many years. Water quality in such closed watef area is changed by outside disturbances (wind, solar heat, etc.). An experimental investigation of turbulent structures induced by wind action in the area which has a two layer system was carried out in a laboratory wind-wave tank. Such closed water area, on one hand, has ecosystem diversity. Especially in warm climate areas, various water plants grow by the shore of the closed water area. But it is considered that the water plants which cut a part of wind play an important role in the turbulent structures. Hence the experiments to clarify the relationship between the water plants and the turbulent structures were performed. In the experiments, the water plants imitated by a styrene foam were set afloat in a laboratory wind-wave tank. And it was divided four types by the covered rate of the imitated water plants to compare. Results of the expetiments indicate that the existence of the water plants contribute to make a significant effect on the scale of the turbulent structures. lt is also studied that an increase of the rate of the water plants reduces its scale gradually.