Movie from late 70s, saw on HBO, cartoon/live-action
I've been trying to figure out the name of a cartoon/live-action movie I saw as a kid forever. I saw it on HBO in the late 70s around the same time Dot and the Kangaroo and that other Dot movie were playing also.
The movie starts with live-action. There is a poor boy I think--they speak in British accents. Anyway, this boy sneaks into a nice big mansion look for food or something and gets caught, I think. It's all fuzzy. Something happens and the boy ends up falling in a stream nearby and everything goes to cartoon. There is a long adventure under the water with seahorses, crabs, and fish. I think the boy still looks like a boy only cartoon. Anyway I can only remember one song they sing, Hi ho balorum or something that sounds like that.
Does this ring any bells with anyone? I would love to watch this again. If only I knew the name of the darn show. Thanks! :)