The water travels at different speeds along the length of the Niagara River. South of the Falls where the river is wide and slow, the maximum speed is about 40 km/h. Near the brink of the Falls, a speed of 109 km/h has been recorded. As the water travels through the Whirlpool Rapids at White Water Walk, it is traveling at about 48km/hr or 30mph, creating the Whirlpool Rapids - "Class 6 white-water rapids".

Rivers are rated on a scale of 1 to 6 in eastern North America, and 1 to 10 in western North America. The Colorado River is the benchmark for white-water, where some sections are Class 5 and 6 and the flow is 60,000cfs.

The Whirlpool Rapids consist of 4 kilometers of 3-5 meter standing waves, making this stretch of whitewater the largest/finest series of standing waves in North America. These standing waves are thought to be caused not by rock obstructions on the bottom of the river, which is probably swept clean here, but by the sheer force (volume and speed) of the water being forced through the narrowing of the gorge at this point.