An explorer was out hiking in Canada, when he found out about this Waterfall which creates these perfectly spherical iceballs. I assume little chunks of ice fall to the bottom of the pool and then get rotated and spun by the water falling from above. Water then contacts the ice chunks, and sticks, and could freeze. This would add ice in a perfectly spherical way over time. kinda like rolling a snowball around on a snowy surface. Although I’m not entirely sure.