Crunch. That’s not the sound I wanted to hear at the back of a dark sea cave underneath a basalt headland pummeled by ocean swell. As the stern of my kayak banged into the rock wall, I paddled forward, hard, as the next swell came through. Not hard enough. The wave pushed me against the cave wall. I pushed myself …

I’m dozing, when high-pitched screams followed by angry whistling tugs me away from my nap on the warm sand. Through binoculars, I spot three crow-sized birds, taking turns dive-bombing a bald eagle perched in a tree on the nearby point. Each dive-bomber lunges, screaming, at the eagle, only to pull up at the last moment, and fly back up to the heights while its …

The bow of my kayak digs a groove into the sand, and I get out and stretch. Maria sheds her dry suit and takes off running down the perfect, uninhabited two-mile crescent of warm sand. Bruce pokes around in tide pools. I wander up the beach, following wolf tracks. An eagle whistles from the trees. Somewhere in the bay I …

“We’re going for Door # 2,” Maria announces. “We think there’s enough space between the icebergs and Gateway Knob.” We push off and row against the strong current of the Alsek River. A moment later, we’re squeezing a raft between the island and a set of massive icebergs, while the current tries to yank us into a whirlpool of exquisite …