Difference between Sell someone down the river and Send someone down the river

sell someone down the river —(coll.) let a person down; betray smb.:

• It’s my considered opinion, John, we’ve been sold down the river.

send someone down the river —(coll., also: send someone down) send a person to prison:

• He had overheard Miss Jones threatening Mr. Dee “to send him down the river for life.”

See also: row someone up Salt River / send someone up the river.