"How do planes fly?"
"How does our fridge work?"
"Can I breathe underwater like a fish?"
Oliver is a curious explorer, so he asks a lot of questions.
Then, one day in the bathtub, he hears a strange gurgle. "What lives down the drain?" he wonders. Soon Oliver is headed down the drain in his homemade submarine on a spectacular mission. But will this clever inventor be able to discover a way back?