"GRR"
Sounds rather like a sound a bear might produce, and indeed, the name of the attraction is Grizzly River Run.

 

 
The "ride" itself (Disney prefers to call its rides, "attractions" in that with the combined theme-ing, they are more than simply "rides") has some interesting facts:
- Grizzly River Run (GRR) is loomed oveer by the man-made Grizzly Peak, center of the Grizzly Peak Recreation Area of Disney's California Adventure (DCA).
- The Run (sounds better than "ride") is the fastest simulated river rapids ride in the world.*
- The Run is also the highest simulated river rapids ride in the world, having a conveyor lift height of nearly 50 feet (click here for a pic showing rafts on the conveyor lift, the peak itself and some of the buildings in the queue area).
- The Run also features the longest and highest drop (pictured quite well here) of any river rapids ride.*
- Rafts are spun as they enter the drop, producing a dizzying, wet effect on the way down.
- All rafts on GRR are indeed free-floating, and the number of passengers and weight distribution make each ride unique.
- Rumors abound of a "Ghost Grizzly" that lives inside the cave near the top of the peak.
- A radio station, WGRR, broadcasts from somewhere near the peak, and can be heard playing "Today's best rockin' country" while in queue for the Run.
- Maps in the ranger's offices and raft guide's offices show sections of the South Fork of the American River.
- The actual name of the river in the attraction (The Rushin' River) pays homage to another California river, the Russian River.
- The Grand California Resort Hotel, modeled closely on famous National Park lodges (especially the lodge at Glacier Park) is actually located inside the theme park, and serves as a backdrop for GRR.
- The mascot for GRR is a rather cuddly looking Grizzly when he's represented in his "plush" form. When DCA first opened, Disneyana collectors stormed the park and bought up every available mascot, and promptly began selling them on eBay.
- Disney had "imagineers" (Disney's creative experts) spend several months searching California grasslands, rangelands and open areas for remnants of the state's pioneer history, and many of the artifacts seen from the queue of GRR (and Big Thunder Mountain Railroad at Disneyland) are actually authentic pieces.
- The Run's finale takes daring thrill-seeking rafters through a steamy, wet geyser area.
 
 
* Both of these records have since been broken by the Kali River Rapids at Disney's Animal Kingdom in Florida.