Sailboats and sculls skimming across the Charles River Basin here look less than idyllic when one is standing armpit-deep in tepid, olive-green water, ankles anchored in cold, oozing muck.
The burning question for two overturned oarsmen recently - as they scrambled to right a scull before an audience of grinning joggers - was: Just what is in the murky water of the Charles?
According to Paul Hogan at the Massachusetts Department of Environmental Protection, there is still sewage flowing ''unofficially'' from storm overflows into the Charles Basin, but ''the river as a whole is excellent.'' There has been ''substantial'' improvement in the past decade.
The Charles begins 25 miles away in Hopkinton, the starting point for the Boston Marathon. It then follows a winding course north, south, east, and west - over 80 miles - before it finally flows past Harvard University and the Massachusetts Institute of Technology into the Atlantic. The Algonquian Indians called it Quinobequin - the meandering river.
Before environmentalists began campaigns to clean up polluted waterways during the late '60s and early '70s, rivers running through industrial towns and past major cities were little more than free-flowing sewers. The Charles was no exception.
The Charles was ''disgusting,'' says an old-timer who used to swim in the river from Magazine Beach in Cambridge as a child. Years ago ''you'd come out of the river with slime all over your body,'' he says.
Even in the '60s, according to Rita Barron of the Charles River Watershed Association, ''one dye company in Needham used to pour out its vats into the Charles and the river actually ran different colors. Some days it was red, some days it was blue, and some days it was green.
''That is what has given the Charles the unfortunate reputation it has today, '' Mrs. Barron says. The perception of it as a dangerous river to swim in because of sewage and other wastes is ''one of the most difficult things we have to work against,'' she says. ''It's so hard to get people to recognize that it has changed.'' She insists that ''the river now is cleaner than ever.''
The river's brown or dark-green color still turns many people away, Mrs. Barron says, but ''it's not all that bad. It's never going to be sparkling clear. You have to realize the Charles drains some 22,000 acres of wetlands. That's like pouring water over a tea bag - you're going to get discoloration.''
The US Army Corps of Engineers recognized that wetlands were the most effective flood control for the river, soaking up water like a sponge and letting it seep out slowly. In 1977 they proposed buying up 9,000 acres of wetlands under a federally funded program. Some 17 sites now are protected.
The lazy bends of the river as it winds through those wetlands in the middle section of the Charles - around Medfield, Dover, and Needham - are the most beautiful stretches, Mrs. Barron believes. ''You'd think you were miles away from Boston. In actuality you're a stone's throw from 128.'' (Route 128 is a major ring road around Boston.)
Indeed, above the South Natick Dam, one almost expects to see a punt with figures in white linen and lace gracefully poling their way through arched bridges and past weeping willows and mallard ducks.
Since 1978, Massachusetts has used specific water classifications. The Charles, says Mr. Hogan, from Hopkinton to the Watertown Dam, is a ''Class B stream'' - suitable for fishing and swimming. (Class A is for drinking only - no swimming.)
Despite the fact that ''everybody was jumping in over the Fourth (of July),'' according to Hogan, the stretch of the Charles below the Watertown Dam, known as the Charles River Basin, is Class C - no swimming allowed because of the presence of sewage.
Most storm overflows, he says, are tied into a system that collects storm and sewage water at two plants below the dam at Watertown and pumps it out to a treatment plant on an island in Boston Harbor. But the ''unofficial'' waste still finds its way into the basin as runoff from salted roads or sewage from faulty pipes.
He says the technology is there to collect all the waste and keep it out of the basin, but tearing up pipes laid in the late 1800s would cost $5 billion. ''And that massive amount of money is just not available.''
There is state money, however, for specific projects. ''Bubblers'' at two points in the basin bring heavier seawater (mixing on the bottom with pollutants) to the surface. The polluted seawater is then flushed out into Boston Harbor through the new $58.7 million Charles River Dam.
Ed Anders, manager of the locks at the new dam, which sits at the mouth of the Charles, keeps an eye on the pleasure boats that pass through the locks.
Would he swim in the Charles? ''No, not right here,'' he says. ''Maybe upriver, in Needham. But the river has improved tremendously.''