John Steve Catilo, a rising senior at the University of Virginia and a former rower at Alexandria's T.C. Williams High School, was eager to help the next generation of enthusiasts take to the water.

So he spent his summers coaching, working with young novices in the Potomac River, where they would learn to row as a team, moving their sleek boats across the river.

Catilo, 20, was working yesterday morning with a boat of nine beginners when the motorboat he was piloting alongside their shell stalled.

"He stood up to restart it. He lost his balance and ended up in the river," said Lt. Alfred Durham of the D.C. Harbor Patrol's special operations division.

Horrified, students took their boat back to shore to call police, and a passing kayaker tried to aid Catilo by throwing a flotation device. But he never surfaced.

Rescue teams from Alexandria, the District -- which has jurisdiction over the river -- the U.S. Coast Guard and the U.S. Park Police launched a search for Catilo, who was not wearing a life vest when he fell into the water about 500 yards south of the Daingerfield Island Sailing Marina near Reagan National Airport.

By late morning, seven divers from the D.C. Harbor Patrol had entered the water to search while rescuers combed the shoreline and a Park Police helicopter scanned from the air, all "working feverishly," Durham said, to find the missing man.

They could not.

Officials called off the search at 2:45 p.m., citing an approaching storm that caused the currents to shift and made it difficult for divers to continue. A recovery effort will resume this morning.

"I don't think it looks good that when we go out there tomorrow we'll find him alive," Durham said.

Catilo's motorboat carried a cushion that served as a flotation device, but no life vests were available for him or the eighth-, ninth- and 10th-grade students he was overseeing, Durham said. Catilo was not required to wear a life vest as he coached. All students and coaches involved in the program are required to be able to swim, school officials said.

Durham said his department will conduct an investigation to determine why oars were the only flotation devices available to the rowers on their scull.

"An oar is not an acceptable flotation device by Coast Guard boating safety regulations," Durham said.

Two weeks ago, the D.C. Council passed legislation that requires children age 13 and younger to wear life vests aboard a vessel unless they are inside a cabin, Durham said. The law applies to any watercraft on D.C. waters, he said.

The legislation was introduced after a 12-year-old German exchange student drowned last year in the Potomac.

"If the victim had been wearing [a life vest], we wouldn't be standing here now," said Durham, who spoke to reporters from a vantage point near the accident scene.

Officials said the current was strong when the rowers began their morning practice, though the waters appeared calmer several hours later. But Durham said boaters "shouldn't underestimate what water can do. . . . It's nothing to toy with."

Catilo's family and friends spent the day at the marina keeping a vigil for the lost rower.

"It's the worst thing a parent or anyone involved in the program could imagine," said Debbie Wells, president of the Alexandria Crew Boosters. Wells got word of the accident shortly after 9 a.m. and raced to the Alexandria schools' boathouse on Madison Street, where the young rowers had access to counseling.

Wells described Catilo as a "very giving person" who loved teaching children to row and could always be relied on to help the program.

Catilo graduated from T.C. Williams in 2001 and had eight years of experience as a rower. He had spent the past four summers coaching in the summer boosters program, which includes T.C. Williams students as well as students from across the area.

"It's a program to teach students how to row," said Barbara Hunter, an Alexandria schools spokeswoman. "They can be novices, they can be at a higher level -- depending on where they are."

At the University of Virginia, Catilo served last year as treasurer of the Organization of Young Filipino Americans, school officials said. This fall, he was to serve as president of the university's Myo Sim Karate and Self-Defense Club. He held a green belt in the martial art.

Staff writers Karin Brulliard and Alice Reid and researcher Bobbye Pratt contributed to this report.

A D.C. fire and rescue boat nears the dock at Daingerfield Island during the search for Catilo, who was coaching novice rowers when he fell into the river. Divers, who called off their search because of an approaching storm, will resume it this morning. John Steve Catilo, a student at the University of Virginia, rowed at Alexandria's T.C. Williams High School.

Parents escort their visibly upset daughter from the Alexandria rowing facility. Catilo and the rowers he was coaching did not have life vests available on their boats.