You don't want to swim through Surprise because you might not get back into your boat before arriving at the biggest and best rapid on Westwater. Skull Rapid is a solid Class IV. It should be scouted on the left — the horizon line is visible from several hundred feet away as the river narrows and is pushed toward the right side of the canyon.

The river surges along the right wall and over or around Skull Rock, a massive boulder that usually creates a big hole that will hold or flip a boat. Depending on the water flow, the run can be done either to the left or right of the rock, but the only way to know for sure is to scout the run in advance.

Even if you make it cleanly through Skull, your troubles aren't over. The most famous eddy on the Colorado River, the Room of Doom, forms during high water at the bottom of Skull's wave train on the right. The current pushes toward a cliff, known as the Rock of Shock. Boats that ram the cliff are liable to wind up in the Room of Doom, a huge, swirling eddy that has been known to capture unlucky boaters for hours. After negotiating Skull Rapid, be sure to pull your boat left, toward midstream or the left bank, to avoid the Room of Doom.

After Skull, the river begins to ease up, but keep an eye out for Sock-It-to-Me, a quick drop with a big wave at the bottom, about a quarter mile below Skull. After that, there are a couple of small drops before hitting Last Chance. This rapid is marked by a big boulder at lower flows and a big wave or hole above 5,000 cubic feet per second.

That's it for Westwater, except for another six miles of flat water before the takeout. The river passes through a beautiful, narrow section before the canyon opens up again. The takeout is at Cisco Landing, a heavily used BLM boat ramp.