This was a movie about a boy that lived in a castle, I think his father may have been king, but the story is about the boy. He finds a pipe or something in the water, I think it may have been in the moat around the castle or maybe it was just a creek. When he finds this pipe he is taken away to another world. He can go to and from this other world. I believe this world is an underwater world. I rember watching it in the late 70's or early 80's> If anyone knows this movie, let me know
