Laser-ablated germanium atoms have been codeposited at 4 K with water molecules in excess argon. Adduct and insertion products, such as Ge(H2O), HGeOH, HGeO, H2GeO, GeOH, Ge(OH)2, HGeOGeH, and HGeGeO, have been formed in the present experiments and characterized by using infrared spectroscopy on the basis of the results of the isotopic shifts, mixed isotopic splitting patterns, stepwise annealing, change of reagent concentration and laser energy, and comparison with theoretical predictions. Density functional theory calculations have been performed on these molecules and the corresponding transition states. The agreement between the experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts supports the identification of these molecules from the matrix infrared spectra. Plausible reaction mechanisms have been proposed to account for the formation of these molecules.