In this paper we present some applications of pseudo-analysis in the theory of fluid mechanics. There is proved the monotonicity of the components of the velocity for the solutions of Euler equations. This help to prove the pseudo-linear superposition principle for Euler equations. The superposition principle is proven also for the Navier-Stokes equations with respect to two different pairs of pseudo-operations. It is proved that Stokes equations satisfy the pseudo-linear superposition principle with respect to a pair of pseudo-operations which are generated with the same function of one variable.