Scrooge and Donald pursue the McDuck millions underwater in ''Hall of the Mermaid Queen.'' In ''It Must Be Magic,'' the Beagle Boys battle a rich prestidigitator. Gyro Gearloose launches a ''Space Food Folly'' in his attempts to invent rations for astronauts. ''Everything's Coming Up Rubies'' when Scrooge and his nephews spar with villainous Flintheart Glomgold in Imdia. Finally Scrooge is almost folled by the Beagle Boys' ''Gift Lion'' .but not quite!.