A day after the rain-swollen Potomac River claimed its sixth drowning victim this year, U.S. Park Police officials said that, apart from installing a human wall of officers along the treacherous 11-mile stretch of river from Great Falls to Chain Bridge, there is little they can do to prevent more drownings.

But federal and state officials, wincing at the news that 23-year-old Alejandro A. Lucero, of Herndon, drowned Sunday after fishing near Great Falls National Park, pleaded with federal judges to issue a court order immediately demanding stiffer penalties for all people who walk, wade or swim into the Potomac from parkland.

Authorities disagreed yesterday on how many of the two dozen teen-agers police rescued Sunday from the Potomac were given tickets. A park service manager could confirm only that four of the youths received $50 fines. They were stranded on islands when rising water covered the rocky path back to shore.

Entering the river from parkland is a federal offense that carries a maximum penalty of $500 and six months in jail. But because of the chaos involved in a rescue and the fact that most offenders are young, authorities usually have either issued no citations or fined violators as little as $25.

"We were too busy rescuing people to write tickets," a U.S. Park Police officer said yesterday. "The water was rising a foot every eight to 12 minutes. As soon as we had some kids to safety, we had to worry about the next group."

Though Montgomery County police were called in to assist in Sunday's rescue, park police are in charge of the federal parkland. Often on a busy summer weekend, when as many as 10,000 may visit the park, there are as few as six park police patrolling the Virginia falls area, according to a park spokesman.

So far, six of the eight U.S. District Court judges in the Eastern District of Virginia have signed a May 13 request by U.S. Attorney Elsie L. Munsell that a federal court order be issued to force future offenders to appear in court.

"This Sunday's incident is just another example of the need for stiffer penalities," Munsell said yesterday, adding that she hoped the remaining judges would sign the order before more tragedies occurred.

Joan M. Anzelmo, a Great Falls National Park site manager, said that despite clearly posted warnings and the widely publicized number of recent drownings, people continue to ignore the danger and wade into the inviting waters.

Apart from hiring an entire army to patrol the waters, Anzelmo said, there is little more authorities can do. "People just have to listen to this message: The river is powerful. Its undertows are deadly. Unless you want to become another statistic -- stay out."

Rep. Frank R. Wolf (R-Va.), who has supported Munsell's recent effort, said yesterday, "It seems like every weekend we're hearing of another drowning. We have got to do something."

Wolf said the expense and danger incurred during helicopter rescues demand that stiffer penalties be levied: "Unless people know that there is going to be a potent punishment, they are going to continue to be carefree."

Park Police officials said that on the average seven drownings occur each each year in the Potomac, but last year 14 persons drowned and already this year, even before summer officially starts, six have lost their lives to the dangerous waters.

Authorities attribute the rising number of fatalities more to the increased use of the parkland fringing the Potomac than to changing conditions making the river more dangerous.

Harold B. Thursby, an Arlington man who served both in the Navy and the Merchant Marine, shook his head and pointed to the dozens of people sunbathing and picnicking yesterday on the rocks at the river's edge at Great Falls National Park.

"People are misled by their own agility or ability to swim," he said. "Look at all those people. They're only inches away from a river that is going 70 miles per hour. Even a salmon couldn't swim against that."

Thursby, a retired federal employe who said Sunday's tragic news spurred his park visit yesterday, said that he believed many of the drownings were caused by the lure of the water's danger. Like many others at the park yesterday, he said he did not believe that even constructing a steel fence along the river would keep people out of the water.

"We're not even considering roping off the river," Anzelmo said. "The national parks were set up for people to enjoy and recreate in a natural setting."