  Magnetohydrodynamic (MHD) ships represent a clear demonstration of the
Lorentz force in fluids, which explains the number of students practicals or
exercises described on the web. However, the related literature is rather
specific and no complete comparison between theory and typical small scale
experiments is currently available. This work provides, in a self-consistent
framework, a detailed presentation of the relevant theoretical equations for
small MHD ships and experimental measurements for future benchmarks.
Theoretical results of the literature are adapted to these simple
battery/magnets powered ships moving on salt water. Comparison between theory
and experiments are performed to validate each theoretical step such as the
Tafel and the Kohlrausch laws, or the predicted ship speed. A successful
agreement is obtained without any adjustable parameter. Finally, based on these
results, an optimal design is then deduced from the theory. Therefore this work
provides a solid theoretical and experimental ground for small scale MHD ships,
by presenting in detail several approximations and how they affect the boat
efficiency. Moreover, the theory is general enough to be adapted to other
contexts, such as large scale ships or industrial flow measurement techniques.
