Labudovo okno locality (50 m-84 m elevation) is situated in the south-eastern part of the edge of the Pannonian Plains, resting along the left bank of the Danube between 1982 km and 1078 km. The investigated locality is the result of rise of the Danube level after dam building of the hydroelectric power station Djerdap I. The vegetation comprises aquatic associations of the classes Hydrochari-Lemnetea Oberd. 1967 and Potametea Tx. et Prsg. 1942. The class Hydrochari-Lemnetea Oberd. 1967 includes the following phytocoenoses: Lemno-Spirodeletum W. Koch 1954, Salvinio-Spirodeletum polyrrhizae Slavnic 1956, Lemno minoris-Azolletum filiculoides Br.-Bl. 1952, Ceratophylletum demersi (So? 27) Hild 1956. The class Potametea Tx. et Prsg. 1942 includes the associations Myriophyllo-Potametum So? 1934, Nympaeetum albo-luteae Nowinski 1928, Trapetum natantis M?lleret G?rs 1960.