Making a Ponyo boat

We watch Ponyo at least twice a week in my house (4 year old loves it) and I have always wondered about the boat. The first thing I wondered if a.) it was real and worked - based on jgc's post seems that it does and might be more common than I thought and b.) if the heat would allow Ponyo to actually sit on the top of the boat as she does while it is moving.

When I made my first pop pop boat, I simply coiled a piece of small hobby tubing for the boiler, with the ends poking through the bottom of the boat.

I don't get how it works. Can anyone explain?

I wonder if the efficiency would be improved if the whole engine construction would be under the surface level.

Nice. This design of creating a toy boat has been extremely popular in south east asia for atleast the past 20 years. It's good to see it here again. Nothing beats nostalgia. :)

Adding this to my list of things to "invent" should I ever be transported thousands of years back in time.

I wonder how I could make a remote control ponyo, low-tech wise ..