THE WATER IS SO COLD that icebergs are floating in the middle. It's June in Wyoming, at 11,000 feet, and Lookout Lake is only half melted. The snow is still five feet deep along the shore, and chunks have calved into the water.

Mike Moe and I have hiked in to climb the Diamond, a 600-foot quartzite face in the Medicine Bow Mountains. People rarely climb here—it's too high, too harsh, too dangerous. There are often snow squalls, rockfalls, route-finding debacles. Mike and I have been climbing the Diamond for 20 years; it's where we train for epics. This summer, 1995, we're going on separate expeditions to Canada: Mike to attempt a ski-and-bike traverse of Baffin Island; me to try a new route on Mount Waddington. This is our last chance to climb together.

Scrambling through the jagged terrain down to Lookout Lake, I feel nimble and at ease. We've done this so many times before, it's as though I'm sliding back through time.

At the water's edge, Mike leaps out onto a flat rock and begins to strip. He stuffs his socks into his boots and plugs them, along with his shirt and trousers, inside his backpack. Then he stands there naked, stroking his short red beard, contemplating the still, black water.

The surface of the lake is a mirror, perfectly reflecting Medicine Bow Peak and its series of stone faces. Here, at the bottom of the mountain, we are still in night's shadow, but dawn is beginning to gild the summit. Long, pink clouds, like giant rainbow trout, suddenly appear in the water. Except everything's upside down, a surreal reflection—as if we're looking at the other side of life.

"Last one to the other side ..." Mike says, and dives into the lake.

It was the fall of 1991, on the Niger River. Diving in from the vine bridge, Mike was immediately swept out of sight. The huge brown river just took him. It had been pouring buckets in Guinea for months and the Niger was swollen fat as a snake that's swallowed a goat, and we couldn't tell how many trees had been pulled into the water that might trap us in our kayaks, so Mike said he'd swim the river to find out. Use his body as a proxy for us and our boats. "It's the only way to test it," he'd insisted. His wife was pregnant and my wife was pregnant and Mike and I were in Africa hoping to pull off one last big expedition before life changed for good.

Mike's done this before, but it still stuns me. The water is so cold it would instantly paralyze anyone but him. Will alone keeps him warm.

I grab his pack and begin hopping boulder to boulder through the snowfield. This is our ritual. I'll hike around the lake, he'll swim across it. We'll meet on the far side, just north of the Diamond.

It's getting light now and the air is a cool violet. I can see Mike chopping through icy water, his feet fluttering. Unlike me, he is utterly unafraid of water. It is his natural element. In high school here in Wyoming he was a state-champion swimmer.

I meet him on the far shore. When he comes out of the water, he's so frozen his skin is a waxy, translucent blue and his movements are jerky. His jaw is clenched and he can't speak, but he's grinning. He fumbles putting his clothes back on; I have to tie his boot laces for him because his fingers are wooden. Heaving on our packs, we continue up through the talus, across a hard tongue of snow.