There is no fluid-flow trickery involved. Dolphins are actually much stronger than human athletes.
According to a study, dolphins produce 10 times more power than the fittest human athletes do.
The researchers used a technique designed to measure the muscle power of athletes on dolphins.
"We used hydrodynamics models that looked at the motion of the flukes (dolphin tails). We found that dolphins could produce very high amounts of power," said lead author Frank Fish, head of the liquid life laboratory at West Chester University in Pennsylvania, US.
The discovery helps to explain why dolphins seem to swim with ease next to boats propelled by powerful engines, said the study published in the Journal of Experimental Biology.
In the experiment area, dolphins produced 549 watts of energy.
When they accelerated the speed, they generated a surprising 5,400 W - making them 10 times more powerful than the fittest human athletes, said the study.