"In Australia the tub water drains differently"
It is assumed that the Earth's rotation causes the water to drain clockwise in the Southern Hemisphere, and in the opposite direction in the Northern Hemisphere (some say even the opposite). But the whirlpool is too small and too fast to be influenced by Earth's rotation. Direction of the small vortex depends solely on local factors such as agitation of water, surface tension or room air circulation. Also at the Equator, the water does not flow directly, but forming a vortex. But, in the depression moves really backwards movement of the Earth, and in the southern hemisphere moves clockwise, at northern hemisphere moves counterclockwise.