Student project to build a radio remote controlled submersible.
They only had a few weeks to do it in, and a very limited budget. They were also mechanical engineering students, so with very little knowledge of electrics. (Though some might argue they have bugger knowledge of anything engineering, but that’s another matter!)
However it does combine the skills of electronics, electrical and mechanical engineering together.
Although radio waves are not good at penetrating water the depth and distance they were working across was not great so it did work quite successfully.
Small bilge pumps were adapted to take propellers which made it a manoeuvrable device.