>>... They let him down the water.
>>
>>"They sold him down the river"?
>
>The meaning of the phrase is literally what it says, or "let the water carry him downstream", i.e. given up on him and let him go down.

I assumed you were doing a literal xlation of a Serbiam expression. It doesn't exist in English, so I gave you the English equivalent. Besides, you wouldn't say "let him down the water"; it doesn't make sanse (esp. as "let him down" means "disappoint him" or "lower him down (gently)"), so "let the water carry him downstream" is te most practical way of saying it, afaik