Dolphins prove that they rely on muscle power, rather than a trick of fluid dynamics, to race through water at high speeds.
Writing in the Journal of Experimental Biology in 1936, British zoologist James Gray made a simple calculation based on observations of a dolphin swimming alongside a ship in the Indian Ocean. The dolphin, he reported, had passed the vessel, from stern to bow, in 7 seconds. The ship was 41 meters long and it was moving at 8.5 knots. “This dolphin must therefore have been travelling at 20 knots [10.1 meters per second],” wrote Gray, who concluded, after an avalanche of more complex calculations, that dolphins couldn’t possibly have attained that speed using muscle power alone.