Yesterday, a couple went out boating on the Des Moines River. They had engine trouble, drifted down and went over a dam. The couple were trapped in the swirl that the water coming over the dam creates. The man died. A construction crew harnessed up a worker and lowered him to the water with a crane where he rescued the woman after attempts to reach her with a boat failed. Without them, it is likely that she would have eventually drowned. There’s video of the rescue and a comment from the rescuer (after an ad).
Here’s the risk explained by the Tennessee Wildlife Resources Agency.
The water can have enough power to hold you and your boat under and pin you there. The rescue boats could not get to her without being pulled in themselves.
Rescuing someone trapped in the turbulent boil is very rare.
–Capt. Steve Brown, Des Moines Fire Department