An interesting project for heating a small enclosed space. Note there must be provision made for a safety valve / expansion escape mechanism. The same basic mechanism could be adapted to a large stainless steel water reservoir. A water depth gauge would also be handy. This is a clip that demonstrates the snowmobile tiny cabin camper: It could be adapted to an ice hole fishing shack.
I don't know that I would want to build a roaring fire on an iced over lake, but maybe you could haul out some kind of fire box to isolate the heat. But then you could just put a wood stove in the fishing shack.