Falaco Solitons
Do try this at home!
Falaco Solitons are long lived topological defects in the discontinuity free surface of water. They have remarkably long life times and will persist for 15 to 30 minutes. The black disks are created from the Snell refraction of a surface of rotational symmetry with negative Gauss curvature.
Weird that I’ve never noticed or heard of these things before.





Really want to try this in a pool now.
Also want to ask developers of fluid physics engines, ‘How accurately does it model Falaco Solitons?’ just to be annoying.
Can’t wait to show this trick to my 2 year old, next bath time!
I just have to convince him it’s going to be exciting enough to justify having a bath without bubbles.