The phrase that is translated as “unstable as water” or “turbulent as water” is not a natural Falam Chin comparison and is conveyed as “like a mountain stream rising and falling.”
Verse: Gen 49:4
פַּ֤חַז כַּמַּ֨יִם֙ אַל־תּוֹתַ֔ר כִּ֥י עָלִ֖יתָ מִשְׁכְּבֵ֣י אָבִ֑יךָ אָ֥ז חִלַּ֖לְתָּ יְצוּעִ֥י עָלָֽה׃ פ
Retrieving the verse