Results of a search for ultra rapid flux fluctuations of galactic sources of maser emission in the water-vapor line at a wavelength of 1.35 cm. An observational technique of a search for ultra rapid flux fluctuations has been developed. From 2002 to 2009 a number of observational sessions for about 40 maser sources have been carried out. Several of them have demonstrated such a variability. Possible mechanisms of the variability are discussed, among them internal processes within the sources themselves as well as external ones, including the theoretical possibility of a resonant effect of gravitational waves from galactic objects on the maser region. Clear evidence for the presence of such a variability has been found in several sources (Cep A, W43M3, W49N, W33B). This variability appears not permanently, but only certain states of particular H2O masers. In some sources (Ori A, W3 OH, W49N) demonstrated any variations by linear polarization of signal. For the Russian authors this work was supported by the Russian Foundation for Basic Research (08-02-01179).