Infrared spectra and intensities of the nu(3) band of H2O in Ar-H2O and O-2-H2O complexes have been studied by helium nanodroplet spectroscopy. It was found that the H2O molecule rotates almost freely in both the Ar-H2O and O-2-H2O complexes. Infrared intensities of the nu(3) band of H2O in these complexes were equal to that of an isolated H2O molecule within experimental errors. The obtained infrared spectra and infrared intensities were compared with those of the N-2-H2O complex in helium droplets, which we recently reported.