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Rivers, or sections of rivers, are classified into six different levels of difficulty to help whitewater rafters choose the right rapids for their skill level. From smooth, easy waters to the most dangerous rapids in the world, the classification levels cover all types of water.

How Classifications Work

The six classes, from Easy to Extreme, can be described in general terms, but even within each class, there is variation. A Class III rapid, for instance, may be on the easy side or on the more difficult side of the level. An easier Class III may be called a III-, while a harder one, bordering on Class IV, might be termed a III+. Some rafters may simply refer to them as an easy Class III or a difficult Class III. The same system is used for Class IV rapids, while Class II has only a II+ designation. At the Class V level, the distinctions become more granular; rapids are referred to as 5.0, 5.1, 5.2, and so on in that manner, allowing for the more complex nature of these very advanced rivers.

Each classification is described by the speed and predictability of the water, and the type of obstacles that exist in that section of the river. The higher the classification, the more skill is needed to safely navigate it.

  • Class I: Easy. The easiest to navigate for beginners, Class I rapids may have a swift current but move smoothly with few obstructions. These waters are easy to swim so self-rescue is almost always possible.
  • Class II: Novice. Expect easy-to-handle rapids that can be managed by most beginning rafters with some experience. These are fast-moving waters with obstructions that can be easily spotted and avoided, and swimmers can usually self-rescue with occasional assistance. Channels are wide and clear.
  • Class III: Intermediate. In this level of rapid, rafters can expect many obstructions, some of which are difficult to maneuver. Medium waves and occasionally large ones are seen; strainers, eddies, and strong currents are common. This type of rapid is best for rafters with a good deal of experience. Strong swimmers can usually self-rescue, but assistance is needed more frequently and the danger to swimmers is higher. Ranges from Class III- to Class III+
  • Class IV: Advanced. This level of rapid features very powerful waters, multiple obstructions, narrow channels, and a greater danger to swimmers. The water is very powerful and currents very strong. Fast and experienced maneuvering is required to safely navigate these waters. Group rescues are usually required for swimmers, and these rapids are not recommended for weak swimmers or groups without rescue experience. Ranges from Class IV- to Class IV+.
  • Class V: Expert. Rapids in the Class V level have an open classification system that uses decimal points. A 5.0 is the base level of this grade of rapids, and it goes up by 0.1 as difficulty increases. Class V rapids are recommended only for the strongest and most experienced rafters, and there is a great deal of danger to swimmers in these waters. These rapids can be very intense and go for long stretches, requiring a great deal of physical fitness and skill to navigate safely. Large waves, long drops, holes, and congested chutes are all common obstructions in a Class V rapid.
  • Class VI: Extreme/Exploratory. The most dangerous rapids in the world, Class VI rapids are not often attempted and often difficult to scout, making them unknown and unpredictable. Rescue in this type of rapid is extremely difficult. Only the most skilled rafters attempt these rapids, and even then, the danger is high. A Class VI rapid may be downgraded into a Class V level once it has been explored and successfully navigated several times.