There is nothing quite like actually doing a test and checking the results.
Now the below is not a particurary well done experiment - more a gimmicky tourist experiment - and so the way to (perhaps) better do it is with a larger circular container, and importantly with a smaller water exit hole, so that:
the water can be poured into the vessel in the "wrong" direction (at least a little) and then there ought be sufficient time for the coriolis effect to overcome this 'wrong' water rotation, and cause the water to actually change its rotation back to the "right" direction.
That would be compelling to witness.
If the coriolis effect is insufficient to overcome a small yet visually evident water rotation in the 'wrong' direction, we then need to devise some other experiment to reach that 'truly compelling' resultant (onlooker) impression which our fragile "science virtue signalling" egos so desperately crave...
Assuming for a moment that this "coriolis effect" is in fact real, we need to be able to strictly separate this effect from initial starting conditions, which could e.g. be demonstrated if the effect is able fo ovelcome some other effect, or can be shown to be visibly different from alternative starting conditions, or etc.
Based on personal measurements of Pi π which bring into serious doubt π's "known" third significant digit, can we be certain that regarding this coriolis effect, that we are not just witnessing rotational inertia of the water molecules picking up speed from initial but tiny (thus unseen) starting water swirl? When conducting experiments, it is often the boundary conditions which are of interest and not the steady state (e.g. that we see in the video below).
Enjoy,
----- Forwarded message from Novica Saponja