With over 28 000 species and half a billion years
of evolutionary history, it is not surprising that fishes
have diversified into nearly every possible aquatic habi-
tat and display remarkable adaptations for locomotion
in the three-dimensional underwater environment[13].
So it is certainly natural for engineers to turn to fishes
as inspiration for understanding how to move under-
water, as a source of new ideas on propulsive systems,
and to understand basic principles of unsteady motion
that are not common in current human-designed sys-
tems which emphasize rigid elements and stability.