Search teams yesterday ended the recovery effort for the body of John Steve Catilo, a University of Virginia student who fell into the Potomac River off a small boat near an Alexandria dock and never surfaced.

Citing murky waters and a powerful undertow, Lt. Alfred Durham of the D.C. Harbor Patrol's special operations division said about 4 p.m. that the body was "unrecoverable" unless it surfaces on its own, which could take up to 10 days.

"We've exhausted every means available, everything from using air support to divers to search-and-rescue dogs and dragging the river," Durham said.

"His body was probably relocated from where he fell in," he added.

Catilo, 20, a former rower at T.C. Williams High School in Alexandria, was teaching novices how to row a nine-person shell Friday morning when the six-foot aluminum motorboat he was piloting alongside stalled.

As he stood up to restart the engine, he lost his balance and fell into the river.

The students, some as young as 13 and on the water for only their second day, rowed to shore to call police, Durham said.

A nearby kayaker threw a flotation device where Catilo went down, but he never came up to grab it.

Catilo was not wearing a life vest, nor did he have one on board, as required by law, Durham said. None of the eighth-, ninth- and 10th-grade students he was overseeing as part of a summer boosters program had life vests either, he said.

Hope ran out early yesterday that the enthusiastic crew coach and rising university senior would be found alive, as search teams began referring to a recovery effort rather than a rescue.

Catilo's brother Paolo, 22, wearing a hooded burgundy sweat shirt, sat on some rocks yesterday by the windy waterfront near where the sibling known as John Steve went down. With his head covered, he stared at the turbulent Potomac, waiting for news from dive teams. Every few minutes, waves of grief washed over him, and friends sitting next to him would put their arms around him.

Search teams from several localities were involved, including Alexandria, the District -- which has jurisdiction over the river -- and Fairfax County, which used a highly sophisticated sonar device that was purchased recently. The same technology was used to locate victims of a water taxi that capsized in March in the Baltimore harbor. Authorities also used dogs trained to sniff cadavers through the water.

Four divers spent much of the afternoon searching the area where Catilo's body was thought to be. But the water was so cloudy that they were working nearly blind.

"Everything is touch and feel," Durham said. "You can't see anything down there."

Catilo was preparing to go to medical school and had talked about becoming a surgeon because of his "steady hands," according to classmate Carlamae Chavez, 20, who met Catilo the summer before their freshman year.

"He always got done whatever he said he would do," said Chavez, who is president of the Organization of Young Filipino Americans, known as OYFA, which Catilo also joined.

Another friend, Cassandra Bradby, 20, added: "He was always studying and always on top of his game. He was one of the most disciplined people I've ever met. . . . When you first met him, he's kind of quiet, kind of shy. But once you get to know him, he really makes you laugh. He really knows how to have fun."

Last year, Catilo performed a dance number that ended in a dramatic pose, with his hands running through his hair. By the end of the semester, he was nominated for a gag category of "best hair" by his peers, said Kareena Balallo, OYFA's former cultural chairman.

"He was a confident, good-natured kind of guy, very relaxed," said Balallo, who is also a rising senior. "When we all found out [about the accident], we were all hoping and praying that we would hear something positive."

Instead, friends and family were told the grim news late yesterday afternoon when the search was called off.

The family declined to comment.

In the afternoon, a candlelight vigil was held for Catilo at the Boathouse in Old Town Alexandria. More than 100 people hugged and cried, including young men and women who were T.C. Williams graduates or who had rowed with Catilo. They joined his parents and others in the Alexandria community for more than an hour, praying and singing "Amazing Grace" as the sun set.

Ed Cannon, a T.C. Williams teacher and head boys crew coach, addressed the participants, calling Catilo "amazing" and "joyful" and telling them that that they lighted candles "to symbolize his inner light."

"He is our friend, our brother, our student, our rower, our coach," Cannon said. "Feel the joy that he always expresses. Let us support each other."

The youth crew program of the summer boosters program, which includes students from T.C. Williams and elsewhere, has been suspended until July 6. The adult crew program will resume to prepare for a meet during the Fourth of July weekend.

Tomorrow, counselors and coaches will be at the boathouse to offer counseling and answer questions about water safety.

Family and friends huddle on the Potomac shore as the D.C. Harbor Patrol, saying rescuers had "exhausted every means available," ended the search for John Steve Catilo.Jessica Golliday, second from left, and Alexandra Knezo, right, join family and friends of John Steve Catilo for a sunset candlelight vigil at the Boathouse in Old Town Alexandria.

John Steve Catilo's friends wait, "hoping and praying that we would hear something positive," as one said.Scott Morgan, an Alexandria rescue squad member, takes Gamble McGowan and search dog Tucker, from Southern Maryland, out to help search the Potomac.Catilo was described by friends as confident, disciplined and good-natured and as someone who "really makes you laugh."