According to Wiki -
a collection of loose, randomly oriented needle-shaped ice crystals in water. It resembles slush and has the appearance of being slightly oily when seen on the surface of water. It sporadically forms in open, turbulent, supercooled water, which means that it usually forms in rivers, lakes and oceans, on clear nights when the weather is colder, and air temperature reaches -6°C or lower. Frazil ice is the first stage in the formation of sea ice. It also forms under temperate glaciers.
And at Yosemite Falls as the winter snow starts to melt, and the waterfalls get turned a into million-litre Slurpee machine, with the slurry behaving like flowing lava. Without as much screaming and bursting into flame, admittedly.
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