A little girl named Judy discovers a hidden cove. As she investigates it, she sees a beautiful shell wash up. She grasps the shell, and soon hears a voice within it urging her to put it back in the water. When she does, the shell grows into a much larger vessel, and in it is a beautiful sea nymph. She tells Judy that she and her other nymph friends are preparing to celebrate Father Neptune's birthday. Judy gets to come along.
