As a result of the unusual temperature dependence of the isothermal compressibility of water at low temperature, the structure factor increases with decreasing momentum transfer, below 0.5 Å−1. We confirm this behavior with a neutron scattering experiment performed at different temperatures and in isochoric conditions. Neutron scattering conditions allow the obtaining of data almost free of the container contribution. The experimental result is in agreement with the theory describing the hydrogen bond network of water at low temperature.