Eyes of the vortex
The vortex in Hayle harbour only appeared a few times a year.
It was a quirk of Victorian engineering devised to stop the harbour silting up. Water would be stored in a pool at high tide and, once the tide had retreated, released back into the harbour to wash away the sand.
The water would get into the pool through a tunnel beneath a quay. But sometimes the tide would come back in faster than the water could pass through the tunnel. This would create the whirlpool.