What is a hydraulic boil in a river?

Answer 1

A "hydraulic boil" is a sucking effect that can occur in the backwash of water that has flowed over a dam, often trapping objects in a cycle that is almost impossible to escape. If you’re stuck in a hydraulic boil:

Keep your lifejacket on, it may be a hindrance while you’re stuck in the boil but it’ll help you when you get out.

The boil will keep pushing you though a cycle, pulling you from the water’s surface to the bottom, over and over again. To get out, you must break out of that cycle. The boil may pull you through multiple times before you’re able to get out. Just keep trying.

Try to get out of the boil by either pushing off of the bottom of the river or trying to swim downriver from the bottom of the boil. Use the river’s energy to help you survive.

Watch out for debris that may be stuck at the bottom of river or caught up in the boil. Source: Steve Isenburg of Fort Worth, past member, U.S.A. Whitewater Slalom Team. Compiled by staff writer Andrew Chavez.