"There are certain limits on swimming speed that are imposed irrespective of power," explains Iosilevskii. One of these is the frequency at which the swimmers can beat their tails to propel themselves forward.

The other is the formation of microscopic bubbles around the tail, a phenomenon known as "cavitation". According to Iosilevskii and Weihs, for animals such as dolphins that have nerve endings in their tails, cavitation can be the most important limiting factor.