This paper proposes the principle of internal gyrodrive for a surface or underwater vehicle. The propulsion force is generated by internally forced oscillations of an elastic or rigid hull. Oscillation torque is created as the reaction torque acting on the hull from a swinging internal high speed rotor with 2 degrees of freedom. The mathematical model is built using computational codes MSC ADAMS and Working Model 2D by adding resistance and added mass inertia forces, obtained by approximation of Solid Works Flow results. The elasticity of the tail part is simulated by the Rigid Element Method – cut-in joints with rotational springs. The stability and dynamical interactions of the system hull-gyroscope-fluid are numerically modeled and optimized. The prototype of a surface vessel with internal gyrodrive shows acceptable agreement with the mathematical model.