A 3D modeling of a fountain on the basis on unsteady Navier-Stokes equations for incompressible fluid. A water jet streams up with permanent initial vertical velocity. Under influence of a gravity it produces a water fountain. The structure of the fountain is unstable. The picture shows the evolution of the fountain. The known technique of dot markers is applied. The numerical scheme implements pressure correction method. The problem is solved in a frame of "Research in Brussels" grant in 1999. Code ASTRA.