Easy. Fast moving water with riffles and small waves. Few obstructions, all obvious and easily missed with little training.
Novice. Straightforward rapids with wide, clear channels which are evident without scouting. Occasional maneuvering may be required, but rocks and medium-sized waves are easily missed.
Intermediate. Rapids with moderate, irregular waves. Complex maneuvers in fast current and good boat control in tight passages or around ledges are often required; large waves or strainers may be present but are easily avoided. Strong eddies and powerful current effects can be found, particularly on large-volume rivers. Scouting is advisable for inexperienced parties. Self-rescue is usually easy but group assistance may be required to avoid long swims.