Class I - Easy flat water, small waves, few or no obstructions.Class II - Easy rapids, clear channels that are obvious without scouting. Some maneuvering may be required. Class III - Rapids with high, irregular waves. Narrow passages often require quick and accurate river reading.Class IV - Difficult, with narrow channels obstructed by rocks, steep and narrow drops. It might be hard to determine the course, hence scouting is necessary on most occasions. Class V - Extremely difficult, long, and dangerous rapids with highly congested routes, which should be scouted from shore.