A copy editor for The Washington Post's sports section who wrote often for the newspaper about his experiences with rowing and kayaking died yesterday in a kayaking accident on the Tygart River in Marion County, W. Va.

John Francis Mullen, 37, of Arlington was with a friend in Valley Falls State Park when his kayak was sucked underwater for several minutes after going over a 10-foot waterfall, Deputy Kevin Alkire of the Marion County Sheriff's Department said. The friend pulled Mullen from the water and administered CPR but was unable to revive him. Mullen was pronounced dead at the scene, Alkire said.

"Everybody said they were doing what they were supposed to be doing," said Alkire, adding that Mullen was wearing a life jacket and helmet and that the men were using a safety line. "It's just an unfortunate accident."

Mullen's friends and family described a quietly determined man with a rare ability to balance physical challenges with a life of the mind.

"He was a real spiritual guy, really well-read, and the gravitas and the importance of the river, and of nature, was something that was not lost on him at all," said Micah Pollack, an assistant sports editor at The Post who had kayaked with Mullen.

The tall, athletic-looking Mullen had spoken of some close calls in the five or six years since he had taken up the sport, said Pollack, adding that Mullen's love for it -- and for the tight community of paddlers he was part of -- overshadowed the dangers. Among other highlights, he competed in trials for the U.S. Olympic team for the 2004 Athens Games.

"It's totally trite and cliche, but he died doing what he loved," Pollack said.

Michael Wohl, who met Mullen 17 years ago when the two were college exchange students in Austria, recalled his friend's love for words and ideas. "His search for meaning was completely intertwined with his love for sports," he said.

Mullen -- known as "Jay" to his family -- grew up in the suburbs north of Boston. His parents live in Gilford, N.H.

Kurt Mullen described his elder brother as being on a "constant quest" that included a recent interest in surfing. The brothers were planning a surfing trip to Costa Rica.

"I was really excited because my brother and I had never taken a trip together as adults," he said, adding that while he himself wasn't as engrossed in sports, "I just wanted to be with my brother one time when he was doing something he loved."

The younger Mullen recalled being "a typical sullen 13-year-old" when his brother, then 17, implored him to find a passion, pressing books on him and eventually inspiring him to become a writer.

"He was my hero. He made my heart expand, and to think he lost his life today just . . . kills me," the brother said.

Steve Seeber, a kayaker who also had skied and mountain-biked with Mullen, described him as an experienced paddler who "ended up in the wrong place in the wrong position, which can happen pretty much anywhere."

Alkire said that spot was particularly treacherous and that the part of the river has two steep waterfalls. Swimming is banned there and kayakers must sign a release form to enter, he said.

"It's a once- or twice-a-year thing there," he said of drownings in that location. "There is a lot of undertow, a lot of eddies, a lot of overhanging rocks underneath the water."

Alkire said that after going over the 10-foot waterfall, Mullen was pinned underwater for several minutes before going over a second, higher waterfall.

"You get under something like that and the current is holding you down," Alkire said. "It won't let you out until it's ready to let you out."

Mullen had worked full time as a copy editor at the Post since 2000 and part time since 1993. In a note yesterday to staff members, Leonard Downie Jr., The Post's executive editor, described Mullen as "a respected editor" who was "very popular with his colleagues. . . . He will be sorely missed in the newsroom and by readers who shared his devotion to white water."

Friends and family members emphasized that Mullen was no daredevil and that he had a healthy respect for the river. Just last month, in a column, he recalled deciding against kayaking a dangerous-looking river in Colorado.

Still, the water called to him. In a column three years ago, he wrote of "my first look, and plunge, into a roaring hydraulic named Calamity," in a river in West Virginia.

"As I drifted, picking up speed and getting hit by cross-angling waves, I felt what I later realized was the sensation I had when as a boy I jumped a chain-link fence and climbed to the peak of a mammoth water tower, hanging from the outside on a straight-drop metal ladder, to get a night-time glimpse of faraway Boston. It was a hyperfocus energized by pulsing fear, but still you wanted more."

John Mullen, competing in a white-water slalom event last year in Dickerson, was on a constant quest, his younger brother says. "He was my hero. He made my heart expand."