As we lower the temperature of water at a certain point it changes from liquid to solid. Yet under certain conditions it is possible to keep the water in a non-equilibrium, liquid-like phase, called \emph{supercooled water}, thus avoiding solidification. Water in such state may freeze under the slightless perturbation, as stirring it a little. The existence of supercooled water is usually known to the students since the introductory courses, but it seems to be difficult to attest in an elementary undergraduate laboratory. A simple method for supercooling water is, however, readily available. It is this short paper aim to describe such a method in a form that may be readily performed in a teaching laboratory.