When you’re paddling whitewater, few features demand more respect than the stopper (also called a hole, hydraulic, or pour-over). They can slow you down, flip you, or even hold you in place.

In this lesson from our Reading and Understanding the River course, we’ll show you:

What stoppers are and the different types you’ll encounter
How to recognise boil lines, towbacks, and stopper shapes
Tips for making safer choices on the river