I saw this today on Flickr.
The put put boat is a steam powered boat. In this use, they are hand made from either baking pan aluminum or flashing. The boiler is made by cutting and flattening a soda can, folding it, then epoxying in two straws.
I remember building these when I was a little kid. It’s a great way to learn a bit about steam power. And what floats and what won’t. 🙂