Swimmer Nick Irons was in Moline, Ill., this past weekend. The dateline on a story in yesterday's Style section was incorrect. (Published 07/08/97)

"Cue to ducks," the film crewman for "Good Morning America" says curtly. Shivering on a wooden dock on the Mississippi River, Nick Irons glances at the quacking brown bird and her fuzzy babies. It is 6:15 on an unseasonably cold and cloudy July morning, and Irons is about to go on national television. Then he will strip down to his black Nike swimsuit, jump into the muddy, rapidly flowing river and stroke his way about six miles downstream to Davenport.

It's just another day on the river for the muscular, deeply tanned 25-year-old swimmer. Since his father's diagnosis with multiple sclerosis three years ago, Irons has quit his job in TV production and embarked on an odyssey that has seen him swim almost 400 miles of the Mississippi in an effort to raise money to fight the disease. If all goes according to plan, Irons will become only the second person in history to swim the length of the Mississippi.

He began his journey on June 1 in Minneapolis. At his current pace -- around 15 miles a day in two or three two-hour installments -- he expects to complete the 1,500-mile swim to Baton Rouge, La., by Oct. 10.

The only other person to make the swim was Fred P. Newton of Clinton, Okla., who went all the way from Minneapolis to New Orleans in 1930. The pollution from nuclear power plants south of Baton Rouge will prevent Irons from swimming that final leg to join Newton in the record books. But setting records isn't the goal. "It's a double mission," he says of the project he has dubbed "MS4MS." "I'm not just swimming down the river, I'm swimming down the river for MS." Irons got the idea for the swim after visiting his parents in Bethesda two Christmases ago, when he noticed that his father's condition had visibly worsened. "I flew from L.A. to D.C. and looked down and saw the river and thought that would be sort of fun to swim," he says. "When I got home, I saw my father limping more than before. Then on the flight back, I saw the river again and kind of put the two together."

Irons had been out of the water since his 1994 graduation from Boston College, where he was a four-year finalist at the New England Swimming Championships in the sprint butterfly and breaststroke. Last year he began training seriously, swimming up to eight miles a day. In February of this year he quit his TV work, which included stints producing "American Gladiators" and the Grammy Awards, to give him more time to train.

The swim has become a family project. It would be nearly impossible for a lone swimmer to navigate the currents of the vast river and avoid boat traffic. So Irons's 22-year-old brother, Andy, leads the way in a small, inflatable gray boat with an eight-horsepower motor. A 1997 graduate of Skidmore College, Andy delayed looking for theater work in New York to spend the summer on the Mississippi with his brother. Their 26-year-old brother, John, takes time out from his doctoral studies at MIT to update a Web page about the swim (http://www.ms4ms.com). And their parents, Connie and John, manage the finances and other administrative details from their home.

John Irons Sr. continues to practice medicine; Connie is the office manager of his allergy and asthma clinic. His patients are able to track Nick's progress on a huge map pinned to the office wall and through the copies of newspaper clippings scattered around the office.

Nick's friend Steve Skarkey completes the river entourage. Skarkey is spending the summer coordinating hotel and media arrangements and driving the MS4MS van. Skarkey and the Ironses "realized this was too big for me to do alone," Nick says. "Everyone's in on it."

Though Andy Irons says spending day after day in an eight-foot boat is not very stimulating -- he reads Trivial Pursuit cards to keep himself occupied -- he insists there's nothing he'd rather be doing. "This is a once-in-a-lifetime thing," he says. "Everybody thinks he must be insane to do it. Nick's not insane, but this is something only Nick would do."

Irons's mission has attracted attention. He checks in twice a day for updates with Channel 4 in Washington, does numerous local radio programs and meets with a constant flow of newspaper reporters. This day is typical: the "Good Morning America" interview at the crack of dawn, a few hours in the water with a break for a cellular phone interview with a local radio station, another radio interview in the car on the way back to the hotel, and finally a swim right up to the riverside Mississippi Valley Blues Festival in Davenport, where he is greeted by about 5,000 spectators. After making a short speech to the crowd, Irons is surrounded by well-wishers who want his autograph or to speak about relatives and friends with MS. Women wearing MS4MS T-shirts give him hugs. People approach from all sides saying, "You're the swimmer," wanting to shake his hand.

Irons's swim is beginning to raise serious money, all of which is being handed over to the California-based Nancy Davis Foundation. He met Davis, who has MS, last year, and was impressed by the organization that bears her name. His aim is to raise $5 million for research, though he's a long way from that. Still, he estimates he has raised more than $50,000, and checks are coming in every day.

As he swims to Davenport, people sunbathing and drinking aboard cabin cruisers hold out wads of money for Irons's Coast Guard Auxiliary escort boat to collect. On shore, he gathers more donations and sells and signs white MS4MS T-shirts. "The response has been incredible," he says. "People on jet skis and fishing boats will pull up and hand soggy cash to Andy -- whatever they have on them."

Corporate sponsors have also been generous. Boating companies Avon and Johnson Outboards are lending the boat, NBC lent cellular phones for interviews, Nike and Quintana Roo Wetsuits provided gear, Timex gave him a watch, Gatorade and Powerbar shipped crates of supplies, and hotels in almost every town have offered free lodging. "It shows the real niceness of people," John Irons Sr. says. "It's kind of refreshing."

This niceness, the small-town Midwestern variety, is especially novel to Nick. "What really blows me away is when people offer us their cars," he says. "At one marina we needed a way to get back, and a man just handed me the keys to his truck. Living in L.A. for the past few years, that just shocked me." Another shock came when the two Irons brothers and Skarkey went into a Savanna, Ill., bar to ask what time the Holyfield-Tyson boxing match started. The owner recognized Nick and insisted that the three come to his daughter's wedding reception, river-soaked attire and all. "The whole night he was introducing us," Irons says. "He'd say, This is my daughter, this is my new son-in-law, and this is Nick and Andy.' I had to tell him, No -- this is her day.' "

Irons shrugs off questions about soreness and fatigue and instead points out the beauty of the bluffs lining the river or the eagles circling overhead. The only annoyance he admits to are the locks, which are placed about every 30 miles on the upper portion of the river. "I'll be happy if I never see any locks again," he says. "The water pools up in front of them so there is almost no current, and there'll be three- or four-foot waves."

But complaints are few. "This is just something that's so appropriate for him to do," brother Andy says. "I realized it when I saw him standing on top of the minivan talking on the cellular phone. He's just a big little kid."

To donate to MS4MS or for more information, call 1-888-MS4MS97. To order MS4MS T-shirts at a price of $15, call 301-564-4090. CAPTION: Nick Irons, on the Mississippi near Dubuque, Iowa. "I'm not just swimming down the river," he says. "I'm swimming down the river for MS." CAPTION: John and Connie Irons with a map showing son Nick's progress down the Mississippi. Nick is swimming the length of the river to raise funding for multiple sclerosis, which afflicts his father.