Fig. 6: The number and diversity of batoid-inspired robots have increased over recent decades.

Normalized speed is measured in disc lengths (or body lengths) per second^{19,24,40,41,42,44,45,46,47,48,49,50,51,52,53,54,55,56,58,59,61,62,63,68,70,71,73,74,75,76,77,79,80,82,84,85,86,87,120,121,122,123,124}.