We apply a recently developed first principles but simplified molecular dynamics method to the simulation of water at different conditions. The computational simplicity of this method allows its application to systems containing a significant number of molecules, yet still taking explicitly into account the quantum electronic structure of the system. In the present work we simulate a system of 216 H2O molecules with periodic boundary conditions at two different densities (rho = 1.0 g/cm(3) and rho = 0.72 g/cm(3) and temperatures ranging from similar to 300 K to similar to 580 K. The effect of density and temperature on the structure of water is analyzed by means of the partial radial distribution functions g(OO), g(OH) and g(HH). We find an important reduction of the hydrogen-bend peak for water at the supercritical conditions rho = 0.72 g/cm(3), T = 580 K, in good agreement with recent experimental results.