International Grading Scale of River Difficulty Class I Moving water with a few waves and small ripples. Class II Easy rapids with waves up to 1 meter and wide, clear, channels that are obvious without scouting. Some maneuvering is required. Class III Rapids with high, irregular waves often capable of swamping an open canoe. Narrow passages that often require complex maneuvering. Rapids may require scouting from shore. Boaters in kayaks should have the ability to Eskimo Roll. Class IV Long, difficult rapids with constricted passages and often turbulent waters. Scouting from shore is necessary, and conditions make rescue difficult. Generally not possible for open canoes. Boaters in kayaks should have the ability to Eskimo Roll. Class V Extremely difficult, long and very violent rapids. Highly congested routes which always should be scouted from shore. Rescue conditions are difficult, and there is significant hazard to life in the event of a mishap. Ability to Eskimo roll is essential for boaters in kayaks. Class VI Water is at the extremes of navigability. Nearly impossible and very dangerous. For teams of experts only. Close study must be made ahead of time and all precautions taken.