Where the shape comes from
Two marks left in water as it sets — the cracks that run through ice, or the crystals forming on its surface. It is the water radical 氵 with one droplet taken away, which is why it is nicknamed the "two-dot water", and it marks cold: 冷, 冰, 凉, 冬.
汉字 filed under 冫
No published character on HSK Guide is filed under this radical yet. 汉字库.