magnetohydrodynamics is a real field of study that has been researched as a form of propulsion in water, so I guess that Clancy was just following the latest in research. A quick look at wikipedia confirms that there were prototypes made in 1965.

I did a short project on it while at university. One issue we had was that using any DC currents in salt water inevitably leads to the production of chlorine gas which isn't a great idea. We could only test our MHD motor for less than a minute before we needed to stop and ventilate the area!

[1] https://en.wikipedia.org/wiki/Magnetohydrodynamic_drive