The successes of modern hydromechanics and aerodynamics are closely related to the theory of plane-parallel movements of incompressible liquid and gas. The results of this theory are widely used to explain experimental observations and to model natural phenomena, as well as in engineering calculations of the aerodynamics of flight of various aircraft, modes of operation of hydraulic and gas machines, hydrodynamics of ships and propellers; when studying the movement of bodies in water at high speed and the rapid immersion of bodies in water and other issues. The book covers a large number of tasks from the above areas.