You don't have to drive hours to get a whitewater thrill. Confluence Kayaking makes a spur-of-the-moment immersion easy. The business rents inflatable kayaks and gear and hosts weekly instructional classes in the University of Denver's Ritchie Center pool, allowing urban adventurers to test the basics before they shoot the rapids. Once you're ready, hit the short course along the South Platte River through Confluence Park; from there, it's just a splash to bigger water elsewhere.