Dolphins swim by exerting minimum effort, according to a new study. This finding overturns an 80-year-old paradox that argues dolphins are not designed for swimming.

 

By using bubbles in a pool, researchers have concluded that swimming dolphins generate thrust quite easily and have no need to compensate for their supposedly underpowered muscles. To show this, researchers filmed the animals swimming through a curtain of tiny air bubbles. The frame-to-frame shifts in bubble position let the researchers work out how much thrust the dolphins produced.

 

The reason why this is interesting is because it dispels long-held "wisdom" that the physical structure of a dolphin means that it should be unable to swim. This is based on the work of Sir James Gray, who calculated in 1936 that dolphins do not possess the muscle to produce the thrust they need to swim as fast as they do. This came to be known as “Gray’s paradox”. Scientists thought that dolphins somehow reduce drag by creating smooth, laminar flow in water rushing by their skin instead of the usual turbulent flow that a human would produce when swimming. From this, World War Two scientists hoped that by studying dolphins they could improve torpedoes.

 

With the new study it seems that a dolphin’s tail can generate high thrust and power without special drag-reducing tricks, so the paradox is no more. This is shown in the video below: