Comment by fainpul
Reminds me of the fascinating efficiency of fish, where even a dead fish can swim upstream, given the right kind of vortices.
I wonder how much potential for improvement there still is for the human body.
https://fyfluiddynamics.com/2018/07/when-i-was-a-child-my-fa...
IIRC, the backstroke races at the 1996 Olympics were pushing the boundaries of human potential as competitors swam some or all of the races underwater. The optics of an underwater race were not good (ha!). As a result, FINA made it mandatory to surface and compete in actual backstroke instead of underwater dolphin kick.