Thesebirds do all of their feeding, sleepingandnestingonthewater, whenafamily of grebes gets hungry they divesofast that they often startle observers who call them the "Waterwitches".
The movie, directed by Chris Weitz, is stuffed with subplots and characters (talking animals, witches, and water gypsies) who all have a story to tell, and the narrative gets so busy that the plot gets lost.