MHD has no moving parts, which means that a good design might be silent, reliable, and efficient. Additionally, the MHD design eliminates many of the wear and friction pieces of the drivetrain with a directly driven propeller by an engine. Problems with current technologies include expense and slow speed compared to a propeller driven by an engine. The extra expense is from the large generator that must be driven by an engine. Such a large generator is not required when an engine directly drives a propeller.
The first prototype, a 3-meter (10-feet) long submarine called EMS-1, was designed and tested in 1966 by Stewart Way, a professor of mechanical engineering at the University of California, Santa Barbara. Way, on leave from his job at Westinghouse Electric, assigned his senior year undergraduate students to build the operational unit. This MHD submarine operated on batteries delivering power to electrodes and electromagnets, which produced a magnetic field of 0.015 tesla. The cruise speed was about 0.4 meter per second (15 inches per second) during the test in the bay of Santa Barbara, California, in accordance with theoretical predictions.
Later, a Japanese prototype, the 3.6-meter long "ST-500", achieved speeds of up to 0.6 m/s in 1979.
In 1991, the worlds first full-size prototype Yamato 1' was completed in Japan after 6 years of research and development (R&D) by the Ship & Ocean Foundation (later known as the Ocean Policy Research Foundation). The ship successfully carried a crew of ten plus passengers at speeds of up to  in Kobe Harbour in June 1992.
Small-scale ship models were later built and studied extensively in the laboratory, leading to successful comparisons between the measurements and the theoretical prediction of ship terminal speeds.
Military research about underwater MHD propulsion included high-speed torpedoes, remotely operated underwater vehicles (ROV), autonomous underwater vehicles (AUV), up to larger ones such as submarines.