Complex sentence: Pinocchio tries to swim to Geppetto, but is washed underwater while Geppetto is swallowed by The Terrible Dogfish, and not seen again until Pinocchio is himself swallowed thereby.
Split into simpler sentences: Pinocchio tries to swim to Geppetto, but is washed underwater while Geppetto is swallowed by The Terrible Dogfish. Gepetto is not seen again until Pinocchio is himself swallowed thereby.