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Interesting! I wonder what is inside that black hole!

The absence of light I'd say.

A nice explanation. One thing though, when you say 'the vortex 'wants' to keep it's angular momentum' we have to assume there is not conscious volition on the part of the vortex in the water?! What actually maintains the momentum?

The sun has to be out and the water should be very calm. Maybe some photon energy is feeding the vortex to keep its angular momentum because it resonates with the water.