alt Hacker NewsI mean provided there was a distinct surface to see then it could happen if it was strong enough, but the problem with the bucket is it's limited depth. If the bucket was 20 foot tall I doubt you would see the bottom before those structures appeared.
Sounds like a good experiment. That experimenter said that deeper water required faster spinning to draw the vortex to the bottom and that the shapes don't appear until the center of the vortex is dry. So they did some experiments with deeper water but it was easier to make the shapes with less water.