The problem about movement of the rigid cylinder keeping vertical position under the influence of running superficial waves in a liquid is considered. The indignation of a falling wave caused by presence of the cylinder which moves is thus considered. Special decomposition on a falling harmonious wave is used. The problem dares an operational method. For a finding of the original the decision, considering that the image denominator represents tabular function, Voltaire’s integrated equation of the first sort which dares a numerical method is used.