I think the main character in this story is the boy.
he liked to daydream and thought nothing's wrong with doing so. however their parents thought he's insane and had mental illness, since the country they lived in didnt allow citizens to daydream and wanted them to think the way the country wanted them to. so the boy was sent to jail so that they can brain wash him and make him forget about the mermaid. they tried so many things to keep him from thinking his own way the boy finally actually became insane. only thing he could remember and think of was the mermaid, and in search of her, he entered the ocean. in his daydream, he's happy with the mermaid under the water, but actually he drowned.
by the way, does anyone know how to comment on blogger using the app? I'm having hard time finding it out...