[No.] 31 [Title] "Cavey and the Murky Mississippi Mystery" [Original airdate] 19 April 1980 [Synopsis] 
Captain Caveman and the Teen Angels go on a cruise on a riverboat on the Mississippi River. While there, some nuclear material disappears in the river. Captain Caveman and the Teen Angels investigate and discover a river creature. The river creature turns out to be the captain of the ship who plotted to sell the nuclear material to an enemy nation.