Probably the only safe conclusion to be drawn from these
observations is that the flow of water in the vicinity of a body
which is exhibiting undulatory movements of the type performed
by a fish or a dolphin when in locomotion, differs substantially
from that past a rigid body when being towed through the
water, and consequently it is illegitimate to assume that the resistance
to movement is the same in both cases. It is, however,
tempting to go somewhat farther.