An amazing YouTube video about the building and sailing the submarine up a river:

https://www.youtube.com/watch?v=KLEH8RJsYgI

This is a much more effective design that the one I watched a few weeks ago: “Building a DIY submarine” https://www.youtube.com/watch?v=pUba126uzvU

I was thinking that they must have built others before to get this result, and sure enough in the linked blog post it says that it was the 4th, like the swamp castle in the Monty Python movie.

It even has a frikkin’ laser [range finder] attached to its head.

Roger the Shrubber would be proud:

https://montypython.fandom.com/wiki/Roger_the_Shrubber