Old Jack and Salty are listening to the lovely sound of the sea through the porthole on the Rainbow. Jack remembers when he and Little Sailor Sue were on the beach and heard a terrible hullabaloo. In the rockpool, Sheena the Shrimp is trying to have a nap but just can't get to sleep. Sally the Starfish thinks some music will help. What happens when all the rockpoolers join in with their musical instruments?