These oars use liquid metal to provide the inertia necessary for movement in space. Crew members work them like boat oars, swinging them to the front of the ship slowly, then pulling them back at a high speed. Pumps inside the oars push mercury or another heavy fluid to the furthest reach of the oar just before it is pulled back, providing an inertial “anchor” for the oarsmen to pull against.
Oars function in pairs, and each oar is worked by two crew members. Rhythm is critical to working the pumps and oars in unison, and it is common for ships propelled this way to rely on chants or drums.
Mercurial oars do not function in an atmosphere.