Three of four rafters flipped into the Salmon River at Lake Creek Rapids made it back to the boat but a fourth rafter swept downstream died.
The Idaho County Sheriff's Office says boaters on Tuesday pulled the man from the water just before noon about a mile downstream from the rapids and began CPR.
Emergency responders continued CPR while transporting him to a medical helicopter in Riggins, but he was pronounced dead then they arrived.
Authorities say the man wasn't wearing a lift vest and was on a private rafting trip.
His name hasn't been released.