The picnickers and fishermen on the edges of the Potomac River are giving way to lacey ice, and the stewards of the region's riverfront are tentatively calling the year a rare success.

It is the first time in 15 years, they say, that the dark and dangerous waters of the river have claimed no lives. No one died while chasing a tangled fishing line; no kayaker, no wader, no weekend mariner drowned in the roiling currents.

It might be a matter of language, the river's watchers say, that saved them.

Most of the people who drowned in the Potomac in the past decade were recent immigrants, often Asian or Latino, who came to the river for fishing, swimming, splashing, picnicking with family.

In each of the past years, several drowned. After a deadly 2004, when five people died, the National Park Service studied the patterns and discovered that most victims could not read the English-language warning signs.

"These are not just the kayakers, the white-water enthusiasts or the twenty-something thrill-seekers who are dying," said Bill Line, a Park Service spokesman. "Most of the victims were non-English-speaking fishermen. Mostly, they were immigrants. People who are, quite literally, fishing for their dinner. And they don't know how dangerous the river is."

In May, the Park Service posted almost two dozen signs at the deadliest spots along the Potomac Gorge, the 14-mile stretch between the Key Bridge and Great Falls. In English, Spanish and Vietnamese, the signs read "Danger! Strong Current. Strong Undertow. No Swimming. No Wading," Line said.

The Park Service worked with its international affairs office and Vietnamese and Hispanic cultural centers, and it showed the signs to native speakers, Line said.

The Potomac's multicultural visitors pose an unusual challenge for the national park system. With the river so close to an urban area, populations are more diverse, and visits are more casual.

Fishing along the Potomac Gorge on the way home from work is not trekking along the raging Colorado River or fishing on the untamed shores of Oregon's Rogue River. Most of the Potomac's visitors don't come with rock-gripper wading boots or a graphite wading staff.

They are like the visitor who walked past a park ranger on a cold day last month in a puffy jacket, chef's pants and black slip-on shoes and carrying a plastic bucket to sit on and a foam container of worms.

"People show up here in high heels, in dresses, in suits. They come from some fancy event or church and think it would be nice to stop by the river," said Kevin D. Brandt, superintendent of the Chesapeake & Ohio Canal National Historical Park. "People are very casual about this river and constantly underestimate it."

On the Maryland side, Hispanic families often gather along the Fletcher's Cove area with picnic spreads and children who sometimes get into trouble in the water. Brandt has several rangers who speak Spanish and walk the river's edge, approaching families and warning children about the Potomac's dangers.

Over the past decade, Jon G. James, the Park Service's deputy superintendent for the Virginia side of the Potomac, has seen a change in the population on his shore as well.

There, many fishermen are Vietnamese, and staff members who speak that language are rare. So rangers get the fishermen's attention, point to the Vietnamese warning signs and hand out brochures written in their native language, James said.

U.S. Park Police Lt. Tom Neider, who grew up in Glen Echo -- where he used to get off the school bus, put down his books and head straight for the river -- now patrols that area. He compiled the drowning statistics, looking at each site, each incident and remembering his childhood along the river when he realized that the river's population is changing.

"Different people are coming to the river, and not everyone grew up here like I did," Neider said. "It looks so serene. You can throw a stick or a leaf in the river, and it will just sit there. Still. Not moving. It's almost like an illusion. You put your hand in the water on that same spot, and you can feel the strong undertow. That's what gets them."

Signs in English, Spanish and Vietnamese warn of the Potomac River's hidden dangers. Most drowning victims are immigrants who speak no English, the National Park Service says."People are very casual about this river and constantly underestimate it," Kevin D. Brandt, superintendent of the Chesapeake & Ohio Canal National Historical Park, says of the Potomac. Five people died in its waters last year.