Upper Yough River
Check out just a sampling of the named features in this 9-mile (14.5-kilometer), predominantly class IV to V run: Bastard, Triple-Drop, Zinger, Meat Cleaver, Powerful Pop-Up, Cheeseburger Falls, Double Pencil Sharpener. Here's one guide's description of how to run Pop-Up: "Pop-up is run left to right. Death slot is to left of pop-up chute. Run slot left to right and try not to broach on triangular rock" [source: Northeastern Whitewater]. While the jargon may be a bit hard to decipher for the inexperienced paddler, the gist is this: "Dude, if something called the 'death slot' is lurking around, don't screw up."
Interestingly though (and you'll see a theme developing here), most of the deaths on the Yough are along the relatively benign Lower Yough, where rafting newbies flock in droves. Specifically, between 1976 and 2006, 18 boaters died on the Lower Yough, and half of these deaths were associated with a feature known as "Dimple" where an undercut rock sits staunchly in the middle of the channel. Tragically, rafters have become trapped in what is effectively an underwater cave [source: Pennsylvania Department of Natural Resources].
As for the Upper Yough, it's gnarly, but tends to run in a relatively safe way -- meaning that its rapids and drops will throw you around, but it's less likely you'll become pinned like you might on other popular class V rivers.