What mild means:
Class I: Flat with slight riffles. Play Jenga, sip a martini while you float. Who it's best for: People who drive below the speed limit.
Class II: Faster pace, small waves, but still the bunny slopes. Take pictures, go for a dip. Who it's best for: Kindergartners, grandparents, anyone who hasn't rafted.
Class III: Roller-coaster rapids, splashing guaranteed, obstacles possible. Plan to shriek like a little girl. Who it's best for: First-time thrill-seekers.
More mellow trips:
Salmon River, ID: Deep in the wilderness, Malibu-esque sand beaches are perfect for sunbathing, camping, and, well, drinking. Something about a river just beckons a brewski, so following smoking-hot days on the legendary River of No Return with brewmaster tastings and pairings. Beer trips Jul; Lower Salmon River, orangetorpedo.com; Salmon main fork, oars.com
Green River, UT: Amid a million uninhabited acres of desert sit Desolation and Gray Canyons--Butch Cassidy country. Glide past dramatic rock formations, cottonwood groves, and bighorn sheep. On the side, hike to ancient petroglyphs and outlaw hideouts--or keep it mellow with yoga or a landscape photography trip. Best Jun--Aug; utah.com/raft
Arkansas River, CO: If your "mild" is more about what happens after a day on the river, try an inn-to-inn rafting trip. Tackle intermediate rapids by day, then indulge in a hot shower and comfy bed each night, plus dinner out in nearby towns. Milder Jul--Aug; inaraft.com
What wild means:
Class IV: Fast-paced chutes and drops with flip potential. Paddle hard; tell your wife you love her. Who it's best for: Hard-core adventurers.
Class V: If you do everything right, you're smiling--anything wrong, you're not. Hold on for dear life. Who it's best for: Evel Knievel, maybe Laird Hamilton.
Class VI: Niagara Falls (for real). Who it's best for: No one.
More trips for adrenaline junkies:
Colorado River, Grand Canyon, AZ: Crash through nearly two-story waves in one of the seven natural wonders of the world, surrounded by 2-billion-year-old rock walls. Best Apr, Sep--Oct; many tour operators;nps.gov/grca
Selway River, ID: You can count on the Selway for gin-clear water, a natural hot spring, and thrilling drops. Limited access means you'll have it to yourself. We hear the rainbow trout's pretty great too. Best Jun--Jul; arta.org or threeriversrafting.com
Tuolumne River, CA: Three hours from San Francisco, take the ultimate rodeo ride over braided channels in a secluded canyon. The crazy Cherry Creek/Upper Tuolumne stretch isn't for everyone, but the river's other 18 miles are bucket-list material for the rest of us.Apr--Sep (beginner friendly Jul--Sep); oars.com