Ground penetrating radar (GPR) was tested to monitor water infiltration in sand. Water was injected down an 81-cm-long tube placed in a hole, with a piezometer recording the depth of water and a tap valve used to adjust it to 15 cm ± 2 cm above the bottom of the tube. During the 20 min of infiltration, a GPR system recorded a trace every second, with its transmitter and receiver antennae at a fixed offset position on the surface. The signal, enhanced by differential correction, allowed tracing of the evolution of the top and bottom limits of the water bulb in space and time. Comparison with hydrodynamic modeling of the infiltration process and simulated radargrams proved that the GPR reflections traced the wetting front and the saturation bulb. A quantified estimation of the evolution of the top border of the wetting zone is provided.