The pod of idling kayakers waited for the right moment to shoot across a jumble of intersecting shipping and tour-boat lanes on the Chicago River, taking their cue from a guide who signaled it was safe by letting loose a motivational battle cry.
"Are you ready to paddle down the canyon of steel and glass?" shouted Sam Huff, a bearded 26-year-old, enunciating each word with the gusto of an announcer at a monster truck rally.
The eight paddlers in orange and yellow kayaks pushed off through the murky water, dwarfed by skyscrapers and drawing occasional horn blasts from hulking sightseeing boats.
After decades of heaping scorn and pollution upon the Chicago River, the city is opening urban waterways for kayaking and other recreation. Similar efforts are taking shape in other cities, including New York and Grand Rapids, Mich.
In Chicago, that vision is running into the reality that the river is still an industrial superhighway for tows and tugs hauling salt, scrap metal and cement in barges strung together in floating fortresses.
"We're just kind of dodging a tragedy," said Cmdr. Jason Neubauer, commanding officer of a Coast Guard safety unit that helps keep the commercial and recreational traffic out of each other's way.
As many as eight barges a day operate in the city, making several roundtrips. A fleet of water taxis and tour boats makes about 100 daily trips. And now kayakers -- up to several hundred on a nice summer day -- are in the mix on a river with narrow passages and high concrete walls that offer few safe refuges for paddlers in trouble.
No major accidents have been reported, but there have been near-misses, including kayakers getting too close and having to be rescued by commercial vessels, Neubauer said.
Guides for long-established outfitters are well aware of the dangers. First-time kayakers setting off on their own, though, have drawn comparisons to kids playing on railroad tracks or riding bikes on expressways.
"It's a very dangerous thing," said Lynn Muench, a senior vice president at The American Waterways Operators trade association, describing how it can take around a mile for a barge to stop.
"You've got kayakers out there that pull in front of them. And our guys are blowing the whistle, saying, `Get out of the way,' and they sit out there and wave," she said.
Besides the lack of quick maneuverability and blind spots, tugs and tows pushing barges have powerful engines that can pull smaller vessels toward them, especially in narrow channels.
There are other hidden hazards on the Chicago River: blasts of wind ripping through gaps between skyscrapers and sewer and storm water runoff chutes that act like giant Jacuzzi jets, pushing unsuspecting kayakers into the middle of the waterway and into the path of much larger vessels.
"There's times when you'll feel a little uncomfortable," said Huff, who guides groups for Kayak Chicago, which began offering tours in 1999. He grew up in Durham, N.C., and kayaked down backwoods rivers before adjusting to the challenges of paddling in an urban setting.
Huff and other guides working for Kayak Chicago get special training and are equipped with radios to communicate with each other and with barge operators. They also carry air horns, tow lines to pull customers out of harm's way, first aid kits, water pumps and lights.
Other outfitters can be dangerously lax. Veteran kayakers say they've frequently witnessed companies taking novice paddlers out without life vests.
On a recent afternoon, Huff and another guide took a group through downtown, past industrial relics, architectural grandeur and occasional gaggles of geese and other patches of scraggly wildlife.
His colleague, 21-year-old Steven Bourke, warned paddlers to stay on the right, saying, "We're pretty much the bikes on the highway. We have no right of way."
Minutes into the excursion, one first-time paddler lost his balance and spilled into the water. Bourke shot over, emptied the kayak of water and had the paddler back in his seat in around a minute.
"It's not that bad, actually," the rescued kayaker, Ryan Postel, shouted to the others, who looked skeptically at the dark water fouled in spots with Styrofoam cups and other litter.
At points in the river with obscured sight lines, Bourke surged ahead to scout for boat traffic and radioed the other guide when it was safe to bring the group forward. They also kept watch as paddlers took their eyes off the waterway to snap photos of the skyline.
"I think when the first boat rode by, it was a little nerve-racking, but you get kind of used to it," said Postel, a 30-year-old Chicago native.
Chicago plans to open four boathouses on the river to offer more access to rowers and paddlers. The first facility opened in June in Chinatown on the river's south branch. Many large cities are doing the same. New York announced plans this month to spend $7 million to transform a desolate waterfront area of lower Manhattan into a recreational destination for kayakers and others.
Partly to draw kayakers, Michigan is putting the rapids back in Grand Rapids by restoring boulders and gravel that were removed over the past century and a half to aid commercial navigation.
In Chicago, the establishment in July of a harbor safety committee to get all users of the river talking with one another has eased some concerns.
But a lack of awareness on the part of recreational boaters and kayakers still poses a serious problem around the region, the shipping industry says.
Muench, who is based in St. Louis, often watches in amazement from a favorite waterside watering hole in Grafton, Ill., as jet skiers wake-jump behind barges.
"A lot of them don't know the rules of the road," she said. "A lot of them don't understand the basic physics of how big these vessels are and how hard it is to maneuver and stop them."