Neil Jordan's Ondine, full of melancholy and blarney, is set in one of those wee Irish fishing villages that belongs to another time - but then modernity intrudes.

It's part of a fanciful subgenre: the mermaid movie (see Splash, see William Powell and Ann Blyth in Mr. Peabody and the Mermaid), although the beautiful creature that Syracuse (Colin Farrell) pulls up in his trawler's net has limbs and toes instead of fins and scales, and seems to have little trouble breathing the fine misty air.

She doesn't like being near people, though, so the hangdog fisherman hides her in a cottage tucked away in a cove. The place belonged to Syracuse's granny, and a path lined with wildflowers winds down to the water - deep enough to bring his boat up close. The creature's name is Ondine, and she is played by Alicja Bachleda, a Polish actress and singer whose faraway gaze suggests longing, loneliness, and lots of experience in front of the camera.

Like John Sayles' The Secret of Roan Inish, Jordan's movie plays with the Celtic myth of the selkie - a seal that can shed her skin and transform into a human. Syracuse's 10-year-old daughter, Annie (a beaming beanstalk, played wonderfully by Alison Barry), suspects as much; she goes to the library, gets all the books she can find about selkies, and does her research. The clincher: Ondine, out on Annie's dad's boat, sings an ethereal ditty and suddenly the fish and lobsters are practically jumping aboard.

But it's not all whimsy and sea shanties, Ondine. This being a movie by the man who made The Crying Game, Michael Collins, and Interview With the Vampire, darker aspects of human nature enter the picture. Annie is wheelchair-bound, on dialysis. (But whip-smart and funny, too: "This town is what's called sartorially challenged," she cracks, visiting the drab local boutique. "It's a supermodel's nightmare.") Syracuse is separated from Annie's mum, who drinks too much. And Syracuse has his own issues with alcohol. He's been on the wagon, but there's always the danger of falling off. Farrell, whose work since In Bruges gets better and subtler each time out, gives Syracuse a soulful, aching charm.

And there's this mystery woman with the tousled hair, who doesn't seem to belong on land or on water. What's her story? Is Ondine really a fantasy, a folk tale? Or is there some more reasonable - and, perhaps, more perilous - explanation for her presence here, in Syracuse's life?

Ondine answers these questions in a third act that's not entirely satisfying. But the trip there - which includes Syracuse's stops at the confession box, where Jordan regular Stephen Rea, wearing a priest's collar, dispenses wry bits of wisdom - is pretty magical nonetheless.EndText