As Japanese critics pretty much tore apart Tales from Earthsea, Hayao Miyazaki (after years of rifts and skeptical distrust of his son's handling of the movie) unexpectantly was present at its premiere and wrote to his son "it was made honestly. It was good." Goro cried. And it lead to Hayao pouring his heart out to create Ponyo as an apology to Goro.
The Morse Code scene is his direct message to his wife and Goro.