The helical filaments of the thin flagella that propel bacteria do not wave or beat but instead rotate rigidly like propellers! And they are driven by a reversible rotary motor at their base.
D001419:Bacteria / Q000648:ultrastructure; D018407:Bacterial Physiological Phenomena; D005407:Flagella / Q000502:physiology* / Q000648:ultrastructure; D008124:Locomotion