An impending ecological disaster involving a sunken oil tanker close to an underwater volcano sends the city into a panic. Nia’s uncle Captain Abbott is to lead a submarine mission to raise the tanker before it can explode. Admiral Bubbles uses a home-made device to switch his brain into Beanie’s body, and vice versa! Now appearing to be Beanie, Admiral Bubbles puts Beanie in a jar of water and stows away on board Captain Abbott’s ship, intending to take control of the submarine and push the tanker into the volcano. Beanie, manages to escape the jar and into the ocean and discovers the brain-switching device that Bubbles has brought along, and uses it to momentarily change bodies with the goldfish. But Admiral Bubbles refuses to be beaten and switches their brains back and forth in an attempt to stay in control. Beanie manages to trap him with the sub’s remote manipulator arm, and raises the tanker to the surface, to the cheers of Abbott’s crew.