Lady of the Marsh: Fantasy

It was the one year in seven, the year when she and her sisters would go out into the world, find mortal men, and lay with them to get daughters. Six years in seven, they stayed in the swamp, among those of their own kind and the simpler ones, where they got sons and daughters that might or might not have the same talents as they. The sisters who were born of man usually had get that bred true, but those born of the swamp wept marshy tears as nine of ten of their get were born mute and changeless. She felt the skin along her back cracking open, like a snail pecked by a bird. Beside her, one of her sisters croaked in fear--

Inspiration: Well, it is leap year. And woot.com had a shirt design called Lady Out of Water (http://shirt.woot.com/Derby/Entry.aspx?id=10366)
Story Potential: Medium.
Notes: Lots about shape changing ladies, and lots about frog princes, but not so much about the distaff side of that family.