Researchers at University of Tsukuba have discovered that the structure of vortices generated around a swimmer's feet changes with increasing speed during underwater undulatory swimming. Specifically, ...

When humans kick swim through water ... of the jet flow between the two vortices around the foot shifted to a more vertically downward orientation, a shift hypothesized to enhance forward ...

The results revealed that the water-flow velocity increased with increasing swimming speed during the underwater dolphin-kick lower-limb action, generating a strong vortex during the kicking action.