SO ALL MY LIFE, I NEVER PUT a toe in the great inland sea that flowed by my city. Nor did I know anyone who had. Although I've been away from home for 25 years, I've recently come back to write a book about Memphis and the Martin Luther King Jr. assassination. Over the past few months, I've been rediscovering the Mississippi—or, I should say, discovering it for the first time. I'm finding to my pleasant surprise that even as the city's suburbs metastasize into that Bubba Gumped, Olive Gardened, La Quintafied hell that is modern America, another part of Memphis has been trending strongly toward the water again.

One morning in early May, I tandem-kayaked a stretch of the river with outdoor-gear retailer Joe Royer, in the celebrated canoe-and-kayak race he founded 27 years ago—the largest such event on the entire Mississippi, with more than 800 boats racing along the Memphis riverfront (and with all barge traffic officially halted by order of the U.S. Coast Guard). Another afternoon, I went out with John Gary, a dedicated river rat who also happens to run the only biodiesel service station in Memphis. In his well-traveled Striper speedboat, we gunkholed around the city harbor, catching some of the barbecue smoke and live music emanating from the famous Beale Street Music Festival. Steely Dan, the Allman Brothers Band, Koko Taylor, Jerry Lee Lewis, John Legend, and the North Mississippi Allstars were just a few of the nearly 70 acts playing along the river over a single May weekend.

Yes, things were definitely stirring on the waterfront again. But to enjoy Memphis's burgeoning river culture, I knew, was hardly to experience the majesty of the true Mississippi. I needed to go farther and deeper, which is how I ended up calling John Ruskey and putting together a canoe trip with an eclectic group of Memphis friends. An evangelizing river guide since 1998, Ruskey insists that the only way to appreciate the Mississippi—to really get it—is to defy common assumptions about its lethality and to float it for days at a time in nonmotorized craft. It was while planning this trip that I hatched the notion of swimming all the way across the thing. And, quietly at first, I began to prepare for it.

On this glorious, clear night, camped on the sands of Dean Island, I join a couple of the Jameson's drinkers in erecting an exceedingly weird driftwood figure, a cultish mannequin that's very Children of the Corn. Burrowing in the sand, we find all manner of decoration to filigree our River Man—a paint-can lid, a corncob, a bald-headed Barbie doll, a walnut, a feather, a spray can of Fix-a-Flat, miscellaneous bones. The nation's refuse, both natural and man-made, has become our found art.

The Mississippi is far from pristine, of course, but camping here I'm struck by its unexpected wildness, its burly swagger, its feeling of being a foreign place even as it pumps through the familiar heart of America. And I'm wondering how I could have spent my life disregarding something so grand. As Ruskey puts it, "It's never a good idea to ignore a beautiful woman."

We lavish one detail too many on our River Man and he collapses in a heap of cluttered lumber. Coyotes howl somewhere in the canebrake. A crescent moon is launched in the sky, and now the heavy FedEx jets—one, and then another, and another one still—come roaring overhead in a mighty lockstep, dropping south toward the sorting complex in Memphis, bearing the packages of the world.

This much I know: Swimming the Mississippi is one of the stupidest things a person can do. And, anyway, it's probably illegal. But I don't see a way around it now. Tomorrow morning, I'll have to follow through with my plan. To hell with steamboat disasters and the diabolical alligator gar.

I'm goin' in.