濯ぐ
すすぐ · susugu · JLPT N1 · noun
rinse
🚿 濯 = water radical 氵 + 翟; the water radical shows rinsing is done with water
The water radical 氵 marks that rinsing uses water, as in 口を濯ぐ (rinse the mouth) and 汚れを濯ぐ (wash out dirt). Use this to link すすぐ with water.
ゆすぐ · yusugu · JLPT N1 · noun
rinse
💧🚿 Water radical 氵 on the left: 濯ぐ is rinsing things with water
The sound ゆ matches 湯 (yu, hot water), a handy link for ゆすぐ. The trailing ぐ is okurigana, the kana that finishes the verb.