When Lu's light goes out, Lu has trouble attracting food and seeing down in the Deep, so the kids decide to show her a world filled with light - the reef. There they realize that Lu's light didn't go out, it's just covered with mud. / On a sleepover with Zee, Bubbles is fascinated to learn that Zee is nocturnal. Zee can't help it, she goes out to play and look for food at night! Bubbles is so excited about this new discovery that she tries to stay up with Zee to learn about and explore what it's like to be nocturnal.