The characters 江, 河, 湖 and 海 all have the three-dots-water radical.
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The three dots are 水 'water' squeezed onto the left side, so a character with them usually has to do with water: 河 'river', 洗 'to wash', 汗 'sweat'. With two dots, 冫 is called 两点水 and is about ice and cold: 冰 'ice', 冷 'cold'.
