Abstract: The fractal dimension of received echo envelope is a useful parameter in a sea bottom classification procedure. As fractal structure of bottom is believed to transfer onto the shape of echo envelope, fractal dimension may describe properly some physical features of seabed, as surface roughness or complexity of layered structure. The paper presents and compares the results of two methods of fractal dimension calculation from echo envelope given as finite set of discrete values. The first method evaluates box dimension and the second is based on the relation between fractal dimension and Lipschitz exponent, which describes some properties of autocorrelation junction of investigated signal. The obtained results show that at least one type of fractal dimension method may be useful in a sea bottom recognition task.