Fast-moving water with small waves. Suitable for age 5 and above.
Straightforward rapids with wide, clear channels. Occasional maneuvering may be required, but rocks and medium-sized waves are easily missed. Suitable for age 5 and above.
Rapids with moderate, irregular waves. Complex maneuvers in fast current and good boat control in tight passages are often required. Large waves may be present but can be easily avoided. Suitable for those who don't mind getting a little wet.
Intense, powerful, but predictable rapids requiring precise boat handling in turbulent water. Large, unavoidable waves and tight passages demand fast maneuvers. With experienced guides, suitable for first-timers comfortable with swimming.
Extremely long, obstructed, or very violent rapids and above-average endangerment. Drops may contain large, unavoidable waves or steep congested chutes. Suitable for those able to pass a short swim test in rapids and in good physical condition.
For teams of experts only, at favorable water levels, after close inspection and taking all precautions. This class does not include drops thought to be unrunnable, but may include drops only occasionally run.