That's actually quite impressive and it ties into why I started the project. When I was a teenager I read a paper that talked about the drive used by Captain Nemo in Twenty Thousand Leagues Under the Sea. The magneto-hydrodynamic drive† basically tries to push seawater through a set of coils and, as you've said, it's very, very inefficient and currently impractical.
Reading that paper inspired me to look into this and I ended up trying to make a submersible with the limited budget I had. It was very frustrating and I just gave up and ended up trying to make linear actuators for touch sensing instead.