If it's June in the Chesapeake Bay, it must be wade-in season.

More than a dozen communities across the watershed host these waterside events, with some turning into unofficial river festivals. The formula is largely the same: A group of people wades in to the river until they can no longer see their feet. It's a test of water clarity, and the higher the water climbs up their legs and torso as they wade deeper, the better.

This unscientific survey complements the vast array of scientific information available on Chesapeake waterways — which includes real-time monitoring data and annual report cards — and focuses elected officials' attention on the importance of clean water, even if just for a day.

Bernie Fowler started the movement, acting on an idea from his longtime friend, the singer and storyteller Tom Wisner. He didn't necessarily intend for it to become a Baywide force for change. In the beginning, his Patuxent River Wade-In was simply a call to action in his river, an effort to show politicians and reporters how pollution was nearly ruining a Maryland treasure.

Fowler would suit up in his overalls and white sneakers, link arms with others to form a human chain, and wade in until he couldn't see his feet. After taking measurements of the so-called Sneaker Index, the group — about 200 strong — would feast on fried chicken and sing songs.

This year, there wasn't much to celebrate. Fowler only got to 34 inches. It was one inch less than last year. But, 2012 was not a great year for the Patuxent. The University of Maryland's Center for Environmental Science gave the river an F on its annual report card for 2011, declining from the D and D minus of previous years.

"The water this year was about the same as last year," Fowler said after the wade-in. "I'm not suggesting that the river's any worse than last year. I don't think it's any better — we're still trying to hold on to optimism a little bit."

So much has changed for the Patuxent since the 1950s, when Fowler rented boats on Broomes Island to weekend crabbers and fishermen, and hundreds of watermen plied the rivers and creeks of Southern Maryland. Now, Broomes Island is a distant DC suburb with hardly any watermen left. Far fewer boats ply the waters of the Patuxent. And those that do are more likely to be weekenders with jobs in DC than fishermen making a living.

The wade-in has changed, too. It moved from Broomes Island to Jefferson-Patterson Park and Museum, a facility owned by the Maryland Department of Planning. Fowler, who is 89, wanted to make sure the wade-in continued after he was no longer around to organize it.

He no longer wears his iconic white sneakers. After so many wade-ins, he needed a new pair. Fowler said he hopes to donate the old ones to the Calvert Marine Museum.

And something is different about the wade-in's spirit. It was troubadour Tom Wisner who conceived of the wade-in and attended every one, singing "Chesapeake Born" with local school children and extolling the politicians to preserve the great river. Wisner passed away in 2010.

"Tom was the soul of it," said Patuxent Riverkeeper Fred Tutman. "The energy for the wade-in has fallen off a bit. People still come, but they come for the tradition."

Nursing the river back to health seems to be a large hurdle now, but it was not so long ago that Fowler believed a clean river was well within reach.

Nearly 40 years ago, when he was a Calvert County commissioner, Fowler and the leaders of Charles and St. Mary's counties sued the state and the EPA. The agencies were going to allow the fast-growing upstream counties to discharge millions of gallons of sewage into the Patuxent River. The University of Maryland scientists in Solomons Island came to court with hard evidence to support Fowler's eyewitness reports.

The counties won, and the state agreed to reduce the allowable levels of nitrogen and phosphorus flowing into the river. That agreement became the model for interstate cooperation, which eventually led to the multi-agency Chesapeake Bay Program and its multi-state restoration effort.

The university scientists were so grateful for Fowler's contributions that they renamed their laboratory in his honor.

The 1980s were a hopeful decade for the Patuxent. Fowler took his fight to save the river to Annapolis, where he served as senator from 1983 to 1994. Gov. Harry Hughes promised Fowler resources and support. He came out onto the river, looked at the dead oysters, and promised to do all he could to help Fowler save the river.

In the General Assembly, Fowler managed to pass a bill that forbade any of the wastewater plants in Calvert County from discharging effluent into the Patuxent. They instead do land application.

At the 1997 wade-in, Fowler waded out to a depth of 44.5 inches — still the test's high-water mark. It showed that the sewage-treatment improvements upstream were working.

But over the next decade, the Patuxent watershed became one of the fastest-growing areas in Maryland. Southern Maryland grew, too, and roads became congested with commuters heading to the Patuxent River Naval Air Station and Washington, DC.

Upstream areas in Prince George's and Howard counties were also growing fast. In the 1980s, when Fowler started his push for the Patuxent, the watershed had a population of 100,000. Today, it is seven times that. Just by itself, Columbia, MD — a watershed town created in 1967 — has as many people as the whole watershed had then.

Fowler remains concerned about sewage treatment plants. With today's technology and innovations, he said, there has to be a better way to dispose of human waste than treating it and dumping it into rivers. He remains concerned that, under current plans, all of the retrofits of sewage treatment plants in the Patuxent River will bring the nitrogen and phosphorus levels in 2025 to what they were in 2010 — when they were already far too high.

Fowler is trying to schedule a meeting with EPA administrators to explain why that plan will kill the river, and he has enlisted Walter Boynton, a University of Maryland scientist who has worked on the Patuxent for more than three decades, to help him.

Fowler is encouraged to see young people working on Chesapeake Bay issues, but he worries that they will accept the river for what it is today, without knowing the great ecosystem it once was, and could be again.

"The recall of how the river was, even back in 1950, the only record we have of that are voices like mine," he said.