  Having conducted a search for the 22 GHz water vapor line towards galaxies
with nuclear activity, large nuclear column densities or high infrared
luminosities, we present H_2O spectra for NGC2273, UGC5101 and NGC3393 with
isotropic luminosities of 7, 1500, and 400 L_sun. The H_2O maser in UGC5101 is
by far the most luminous yet found in an ultraluminous infrared galaxy. NGC3393
reveals the classic spectrum of a `disk maser', represented by three distinct
groups of Doppler components. As in all other known cases except NGC4258, the
rotation velocity of the putative masing disk is well below 1000 km/s. Based on
the literature and archive data, X-ray absorbing column densities are compiled
for the 64 galaxies with reported maser sources beyond the Magellanic Clouds.
For NGC2782 and NGC5728, we present Chandra archive data that indicate the
presence of an active galactic nucleus in both galaxies. The correlation
between absorbing column and H_2O emission is analyzed. There is a striking
difference between kilo- and megamasers with megamasers being associated with
higher column densities. All kilomasers (L_H_2O < 10 L_sun) except NGC2273 and
NGC5194 are Compton-thin, i.e. their absorbing columns are < 10^24 cm^-2. Among
the H_2O megamasers, 50% arise from Compton-thick and 85% from heavily obscured
(> 10^23 cm^-2) active galactic nuclei. These values are not larger but
consistent with those from samples of Seyfert 2 galaxies not selected on the
basis of maser emission. The similarity in column densities can be explained by
small deviations in position between maser spots and nuclear X-ray source and a
high degree of clumpiness in the circumnuclear interstellar medium.
