Carmen the Crab and Scotty the Puffin are enjoying singing together, but when Bubbles the Whale joins in they can't believe the racket she makes. It's not until Salty the Seal arrives that they discover they are wrong about Bubbles - she can sing beautifully, but only under the water. Meanwhile Nat has invented a new song that he wants to sing to Miss Moo - if only he could find his missing guitar. With the aid of one of his latest inventions, the Detectotrack, and some of Miss Moo's ingenuity they soon find his guitar. But after all that, will Nat remember his song?