Inter-Regional Scale of Whitewater Difficulty
Class I: If you get out of your boat, you just get back in your boat and your friends all laugh at you.
Class II: If you get out of your boat, you grab your boat and paddle, swim to shore, and your friends all laugh at you.
Class III: If you get out of your boat, you get bruised a little, your friends gather up your boat and paddle and they all laugh at you.
Class IV: If you get out of your boat, you get the crap beat out of you, it takes your friends awhile to find your boat and paddle, and they all laugh at you.
Class V: If you get out of your boat, your paddle is never seen again, one of your friends gets to keep your boat, another keeps your significant other, they split your life insurance, and all laugh at you.
Class VI: If you get out of your boat, it's unpredictable what happens to you and your gear, but one thing is sure: your friends will all laugh at you.