It is not unusual to find ice spheres accumulating along places like the Northeastern shore of Lake Michigan during cold winters. The balls tend to form where water turbulence breaks up a layer of slush. Mattes of slush and frazil ice accrete in the turbulent, supercooled water. Where the wave action is strongest, typically near-shore, slush and frazil evolve into spherical lumps. If conditions are just right, they’ll continue to grow until waves push them ashore.