The 1990 film "The Hunt for Red October" (based on Tom Clancy's 1984 debut novel of the same name) featured actors like Sean Connery and Alec Baldwin, but the star of the movie for physicists was a revolutionary new magnetohydrodynamic (MHD) marine propulsion system. The so-called "caterpillar drive" worked with no moving parts, allowing a nuclear missile-armed Soviet submarine to approach the U.S. coast undetected. As the submarine captain (played by Connery) said, "Once the world trembled at the sound of our rockets … now they will tremble again--at the sound of our silence." MHD propulsion is not fictional: real-life prototypes include the "EMS-1," a 3.0-m submarine that achieved speeds of 0.4 m/s during tests in California in 1966, and the "ST-500," a 3.6-m boat that reached 0.6 m/s in Japan in 1979. The world's first and so far only full-sized MHD-propelled craft, "Yamato-1," carried 10 people at speeds of up to 15 km/h during successful sea trials in Kobe, Japan, in 1992. The "Yamato-1" has since been put up on blocks (Fig. 1) and interest in this form of marine propulsion has apparently waned. Why? Motivated by this question, and by the possibility of engaging students with a simple but dramatic demonstration, we built and tested a small-scale MHD boat that can easily be replicated by instructors at low cost in a classroom setting. Our treatment differs in emphasis and is complementary to an excellent earlier article in this journal by Font and Dudley. Other useful discussions are in Refs. 6-10 and a typical textbook account appears in Ref. 11.