Already two hundred years ago, it became clear that the oar both the paddle wheel are less efficient than the propulsion device of a fish. Copying their tail flipper, the engineers imperceptibly got a screw. Screw had been perfected and complicated, the theories for him was customized, but the screw ship still insufficiently effective, whereas its screw worse than created by nature.
Improvement of the propeller - is not the solution, but only a constant reminder of the existence of "Gray's Paradox". But how can be copied the propulsion device of dolphins and fish, when still not entirely clear how it work?