A story in the style of "parent makes bargain and inadvertently must surrender their child." Here, a once prosperous man has fallen on hard times. He encounters a water spirit, who promises fortune as long as he gives her what has just been born at his house. The father agrees, thinking this will likely be a puppy or kitten. However, he finds out as he comes onto his property that his wife has just given birth to a son. I've read variations of this but this is still an interesting and winding tale that does have a couple of twists.