Vortex
Wherever you may be in the Northern Hemisphere, bathtub water will form a vortex as it goes down the drain—almost always spinning in a counterclockwise direction. But in the Southern Hemisphere, the bath water will spin in a clockwise direction as it runs away. One in a few centers of population where the tub’s plug hole is directly on the equator, such as Nanuki in Kenya, will the water run away twisting as often one way as the other or forming no vortex at all.