Walt later wrote the following of his experience on the Alsek:

The severest part of the canyon looks to me shorter than the 12 miles previously reported. I would guess just five miles long. But it's as tough as I imagined. There are two or three good stops for a kayaker, but there is no way to walk the riverbank and scout the worst rapids. There are too many cliffs that are too severe to climb. From the air I saw a way to portage around the toughest spot in the gorge.

Also saw several very impressive boiling pots with water spouting 10 to 20 feet high. I think I can avoid these. There is one eight-foot roller wave all the way across the river that will be a sure flip, but I don't believe it will trap a kayak sideways. A roller like this is caused by a ledge that acts as a dam. The water streams down the nearly vertical spillway and, as it meets turbulent water at the bottom, a huge wave forms and curls backward like a surfing wave. If a kayak turns sideways and doesn't crash through the crest, it will tumble over and over and be held fast in the wave. There are several sure flips but no holding holes and no danger, unless I swim...