The pontoon rounded the narrowest bend of the Anacostia River just as a great blue heron swooped by. Silver and red maple trees towered skyward from the shore, their leaves rustling in the wildflower-scented breeze.

"Hard to believe we're in the middle of a major metropolitan area, isn't it?" James F. Connolly murmured to his colleague Robert Boone.

Boone, standing at the helm, grinned back in reply.

There is much talk about the Anacostia's future these days. District officials are preparing to spend billions to clean the city's segment of the river and transform its waterfront into a gleaming stretch of apartments, shops and parks. In addition, in the wake of several legal challenges, the D.C. Water and Sewer Authority (WASA), has developed a $1.35 billion engineering plan to stop sewage from overflowing into the river from its combined sewer and storm pipes during heavy rains.

But Boone and Connolly -- president and executive director, respectively, of the Anacostia Watershed Society -- want to make more people aware of the many pleasures the river already has to offer. They also want to stimulate public interest in ensuring the river's long-term health.

"Because of the Anacostia's history of being polluted for so many years, there is a whole generation that was taught to stay away from it," Connolly said. In fact -- and attributable in part to the society's efforts -- the river's banks today are substantially free of the knee-deep trash that prompted Boone to start his nonprofit organization 15 years ago. The water quality, however, is still marginal for much of the year.

Removing that debris was the society's first objective, Connolly said. Now, "our goal is to reintroduce people to the river -- to get them to come out on the water and make it an everyday part of their life."

Among the reasons, Boone said, is that it would simply be nice for more people who live along the Anacostia to have a place where they can "reconnect with the natural world and chill out from the stress of life." The river runs for about eight miles from Bladensburg in Prince George's County into the District.

The two environmentalists also confess to a second motive, reasoning that if more residents boat on the Anacostia and stroll along its banks, they will become concerned about the less visible, but far more potent pollutants still coursing through it.

Much of that pollution originates in Maryland, where about 80 percent of the river's watershed lies, which includes land, river and tributaries. A recent study commissioned by WASA estimated that Maryland is the source of more than 60 percent of the organic waste in the water -- including sewage, discarded food and engine oil -- which is often swept into the river by storm water running off paved surfaces.

Because there are so many sources of pollution -- leaking sewage pipes in Maryland and wetlands that have been paved over, to name a few -- cleaning up the Anacostia will require sustained public interest.

"Once people become open to the idea of the river being more than just a trash dump, once you have a constituency of people who have incorporated it into their lives, you have real power to demand change," Connolly said. "We're trying to build that constituency."

Connolly said he was optimistic a proposal by the District government to develop much of the waterfront in the city, which received new support this week from the D.C. Council, would help the overall health of the river. While the prospect for more development does carry the risk of causing more pollution, he said, "people will not want to come to a restaurant on the waterfront if the river is still dirty."

At least once a week, Connolly and Boone head out onto the water in their pontoon with anyone they can persuade to join them -- schoolchildren, local officials, other politicians and, on a recent afternoon, a reporter and a photographer from The Washington Post.

To take the boat trip, which began at a marina in the District just north of the wide channel where the Anacostia empties into the Potomac, was to encounter a surprisingly diverse array of wildlife. There were fierce-looking ospreys raising their chicks in large nests woven from thick tree branches, graceful barn swallows diving in and out of the mud-clump homes they had built under bridges, and tiny turtles sunning themselves on logs.

Also on display as the pontoon made its way north into Prince George's were the many ways the society has improved the river. Grassy riverbanks were cleared of trash during frequent cleanup days. Large paddies of wild rice were planted by society volunteers and local schoolchildren to contain storm water runoff and prevent the shore's erosion. Nets were erected at the society's urging around storm drains leading into the river in order to trap trash.

Finally, at the northern-most navigable stretch of the river, the boat reached its destination: Bladensburg Waterfront Park. Neglected for years until the Maryland-National Capital Park and Planning Commission refurbished it in 2000, the park embodies both the Anacostia's promise and the challenges that remain.

At peak season hundreds of residents come to picnic in its attractive riverbank pavilion, fish off its pier, or rent canoes and kayaks from its boathouse to explore a section of the river so peaceful and pastoral it looks as though it were lifted from a Romantic painting.

Yet a society study indicates that the park is also on the most polluted point on the river. Every weekday during the boating season, the society tests water quality at the park and at the 11th Street Bridge, four miles downstream. In 2002, the most recent year for which results are available, the water at Bladensburg Park was found unsafe for swimming on 86 of 100 days, compared with 36 days at the 11th Street Bridge -- possibly because the river in front of the park gets less of the cleansing tidal water that washes up the Anacostia from the Chesapeake Bay.

As the boat neared the pier, Boone cut the motor and let the vessel drift silently for a few moments as he watched three men fishing from the structure in the water. He had mixed emotions at the sight of them, he said.

On the surface, the scene was exactly what he has been working so hard to promote all these years. But his worries linger. If the men eat too much of their catch, they are taking a risk.

"Our goal is really to have a fully swimmable, fishable river. Someday maybe we will, but we're not there yet."

Trash accumulates in the Anacostia River, above. At right, a waterfowl explores a riverbank amid debris. Below, James F. Connolly , executive director of the Anacostia Watershed Society, discusses a CSX railroad bridge over the Anacostia. "Our goal is to reintroduce people to the river," he said.Robert Boone, president of the Anacostia Watershed Society, shows statistics concerning the river. Below, a view of Bladensburg Waterfront Park from the Anacostia. A study by Boone's group indicates that the park is on the most polluted point of the river, possibly because the river gets less of the cleansing tidal water there that washes up from the Chesapeake Bay.