열 길 물속은 알아도 한 길 사람 속은 모른다

yeol gil mulsogeun arado han gil saram sogeun moreunda [열 길 물쏘근 아라도 한 길 사람 소근 모른다]

열 길 물속은 알아도 한 길 사람 속은 모른다더니 · 열 길 물속은 알아도 한 길 사람 속은 모른다고

you can never truly know what's in someone's heart (lit. you can know water ten fathoms deep, but not a person's heart one fathom deep)

Example

열 길 물속은 알아도 한 길 사람 속은 모른다더니, 그 친구한테 속았어요.

You can never really know what's in someone's heart; that friend deceived me.

Word parts

길 is an old measure of depth, about a person's height. You can gauge water ten 길 deep, but not the inside (속) of a person only one 길 tall.

Good to know

물속 is pronounced [물쏙]. Said after being surprised or betrayed by someone you thought you knew.