The third installment of writer-director Deepa Mehta’s “elemental trilogy” is an agitprop melodrama, and therefore rather as fashionable in today’s America as it is provocative in India—which, with respect to the egregious social marginalization of women that this movie decries, hasn’t changed nearly enough since the late ’30s. That was a time, Mehta asserts, when Hindu orthodoxy held widows in even worse esteem than second-class citizens; they were financially burdensome pariahs. Water takes place mostly within the cloisters of a widow’s ashram, where Mehta discovers some great narrative potential—but diverts from it into a Bollywoodized, by-the-numbers romance between the movie-star-loveliest of the widows (also, reluctantly, the resident prostitute) and the local dashing, two-dimensionally progressive Gandhi enthusiast. Certainly, Mehta has vision and a voice; she’s on to something with the analogy between British colonialism and patriarchal Hindu fundamentalism. But Water too often waters down its own political assertiveness with mawkish indulgence.