But since it came up ... fun fact: water doesn't reliably spin down the drain in the opposite direction in Australia, nor does reliably spin down the drain one way or the other depending on where you are located in the world.
Coriolis effect definitely effects larger scale things like hurricanes, but local influences easily overwhelm its effect at the scope of a bathtub drain. Things like existing currents in the body of water, irregularities in the surface of the drain, etc ... are much more pertinent. The very same drain might spin the water one direction on one day, and the other direction on the next day, in fact.
You have to set up very specific controlled conditions in order to see the Coriolis effect at such a small scale. If you DO set them up, though ... you will in fact reliably see said difference.
Another interesting 'point' about the phenomenon is ... it's kinda just a matter of 'perspective'. If you use the perspective of the Northern Hemisphere and observe that a Hurricane spins 'counter-clockwise', and then you observe one in the Southern Hemisphere and say it's 'clockwise', the reason it seems this way is because you're maintaining the 'Northern Hemisphere' perspective when determining they spin 'opposite ways'.
In another way of thinking, they're 'spinning the same way' relative to the equator. The way they spin are essentially 'reflections' of each other. Kinda like if I point at you and make a circle with my finger and say 'i am drawing clockwise or counter-clockwise ... you will say the opposite of what I would say (unless you stop and consider the view from my perspective and change your answer on that basis).
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