A standing wave with a tumbling crest.

A large standing wave caused by deceleration of current.

a big, unstable standing wave

A very steep wave.

A wave in a river formed by obstacles on the river bottom, where the wave stands still relative to the bank.

A rhythmic series of waves caused by the convergence of main channel currents. Results from rising water, underwater obstacles or ledges, or an increasing river speed. Forms downstream of a gradient. These waves can be fun to ride, but can also be large enough to swamp an open canoe. See Standing Wave.