I remember seeing this move in the late 70’s where a boy who likes fish and was not popular at school.
The boy jumps into the sea and becomes a fish.
His parents think he is dead. His father recognizes his son as a fish while standing on a ship and looking into the water. The son (now a fish) had glasses (spectacles) on.
I was in 3rd or 4th grade. I cannot find anyone who remembers this movie. Does anyone know what I am talking about?