Even if you're not a boardsailor, Turnagain Arm is worthwhile. I spent one windless afternoon hiking the aptly named 3,550-foot Flattop Mountain on the southern edge of Chugach State Park. Abutting the northern shore of the Arm, the half-million acres would probably merit designation as a national park anywhere else. It offers 8,000-foot peaks, streams packed with game fish, some of the world's last remaining ice fields, 200-plus miles of trails, and a ski season that lasts well into May.

Although the elevation gain on the 3.5-mile round-trip up Flattop was only about 1,500 feet, the trail's plenty challenging—especially at the top, where the steep rock outcrops require a mix of scrambling and light climbing. At the summit, Iwas rewarded with spectacular views of Anchorage to the northwest, and the Kenai Peninsula to the south.

"Some days it's hard to pick your poison," boardsailor Janet Tower admits. "If you're into mountain-biking, there's endless singletrack that can take you for miles without seeing another soul. My favorite is Moose Trail, right off the Seward Highway along the Arm. But be sure to wear a bear bell on your bike—just because you won't see anyone else doesn't mean you're alone."

Like Tower, many of the sailors I met cram in one or two other sports after work. And all that's before going boardsailing at nine—at night. Astonished by their stamina, I asked, "When do you guys sleep?" The answer was always the same: "All winter!" —T.B.