[apendleton]

This paper doesn't propose propelling the boat magnetohydrodynamically, but rather using magnetohydrodynamics to alter the movement of the water around the boat to reduce its drag. MHD for propulsion has been doable for a long time (anecdote: someone built a small MHD drive for my high school science fair). Turns out they're pretty inefficient, so not very practical.

Also, as an aside: MHD propulsion was only the mechanism that powered the sub in the movie. In the book, it was an impeller.