This article discusses the problem of property and use of waters and the legal aspects of the definitions of lakes in particular. To achieve this, the authors reviewed the acts on Water Law from 1922 up to the present day. They proved consistency in the application of the water law. From the hydrological point of view the lake belongs to stagnant waters. The definition included in the Water Law act is contrary to this depiction of the lake. The act reads that the lake may be classified as stagnant or flowing water depending upon the existence of the natural, permanent or seasonal, inflow (or outflow) of the lake. This obviously constitutes a discrepancy between the scientific and legal definition of the lake.