JULIA MANCUSO JUST LEAPT off a 45-foot waterfall. Now she's treading clear blue water below, trying to convince me to follow. "Jump hard and tuck your arms and extend your legs before you hit," she calls up. I don't think so. "I'll just walk around," I yell back, scanning the jungle for an escape.

"This is the only way out," she says. "But don't worry—it's easy!"

So far, nothing about my day on Maui's north shore with Mancuso, 23-year-old phenom of the U.S. Ski Team and part-time Maui resident, has been easy. We started with a hair-raising drive in her pickup along the switchbacks and single-lane bridges on the road to Hana. Then it was a punishing slog up what locals call the Commando Hike—a shallow river littered with felled trees and one very puffy feral-pig carcass—and into a pitch-black lava cave full of deep pools. "This is where we put on our war paint," she said, smearing mud on her cheeks after we'd swum across the third pool. "Why?" I asked. "Are we going to war?" Mancuso grinned, then led me up a 20-foot free climb to the cave's exit and halfway across a wooden suspension bridge, where we jumped 25 feet back into the river before reaching my current point of no return, at the top of the waterfall.

"Just do what I do in the starting gate," she shouts, trying to coach me over the edge. "Clear your mind, take a deep breath, and go."

This ritual has sure worked for Mancuso of late. At the 2006 Olympics, in Turin, she took a deep breath at the top of the giant slalom and went from longshot to gold medalist. She followed that with a breakout performance on last year's World Cup circuit—four wins, ten podium finishes, and third place overall—while recovering from surgery to remove a painful bone spur on her left hip. This year, she's favored to become the first U.S. woman to win the overall World Cup title since Tamara McKinney, 25 years ago. But even if she does that, she'll still be only halfway to her goal: Ultimately, she wants to be seen not just as a skier but as an icon of the year-round adventure lifestyle—think Laird Hamilton in a bikini—whose marketability extends far beyond the slopes.

Me? I just want to get off this waterfall. After ten minutes of whining, I jump. But in the air I freak out and ball my legs into my chest and—smack!— hit the water painfully like an oblong coconut. Mancuso can't stop laughing. "See?" she says. "Easy!"