It is a glorious, sparkling day on the Charles River, and I am in it.
I float in the warm, choppy water. The T slides across the Longfellow Bridge to my right. Runners cross the Mass Ave. Bridge to my left. Boats bob nearby. The city looks lovely from this angle.
Fa-la-la. This is quite pleasant.
Only, a couple of people on the Esplanade are looking at me like I am completely barmy.
Nobody swims in the Charles.
First of all, it's illegal to just jump in (I took a kayak out and, uh, fell off it).
Second, a lot of people wouldn't be caught dead in this river.
Maybe it's the industrial waste dumped into the water by the factories that sat on its banks for more than a century, leaving the sediment packed full of mercury, pesticides, and other toxic delights.
Or the zillions of gallons of raw sewage that were pumped directly into the river starting in the 1840s.
Or the blooms of skin-irritating, nausea-inducing blue-green algae that have popped up the past few summers.
Would Lila Hamill of Medford hop in?
"I would get in it for, like, money," she says, from the safety of the bank on the Boston side.
"I would," says her friend Vicki Mountain of Arlington. "If I was on fire."
Those attitudes break hearts among activists and officials who have spent 20 years and hundreds of millions to clean up the Charles.
The factories are gone. It's illegal to dump waste in the river. Much of the junk has been fished out. Sewage is sent to Deer Island now.
Sure, there is plenty here to feed the old rep: that algae, for one thing. And the sediment, which will always be full of really bad stuff, and shouldn't be stirred up. And heavy rains still overburden city sewage pipes, sending overflow into the river.
But last year, the Environmental Protection Agency gave the Charles a B++ for cleanliness, meaning it's safe for boating all of the time and safe for swimming most of the time.
"The Charles used to be a stinky sewer, and it's really turned around," says Ben Martens, Swimmable Charles coordinator for the Charles River Conservancy, which promotes public use of the Charles River Basin. "It's a success story you don't see very often."
But nobody seems to know about this huge achievement, and swimming here will still get you a $50 fine.
So the Conservancy has begun these annual 1-mile Charles River swim races, starting from the dock by the Arthur Fiedler statue, in the hopes that the public will see the much-maligned waterway differently. The first race, in 2006, was done in by an algae bloom. But last year's was a big hit. This year's race is scheduled for today.
Martens and the others have visions of new urban swimming spots off docks, or in protective pools suspended above the sediment.
Until the 1950s, hordes of locals crammed Magazine Beach in Cambridge and other places along the Charles, ignorant of the toxic soup they frolicked in.
What heaven it would be if we could do what no other American city has managed so far: Make our urban river a bather's delight and return to the vibrancy of those days - without the toxic part.
We're almost there.
But the next steps might be as complicated as cleaning up the river.
The Department of Conservation and Recreation, which runs the parks that line the river, has been listening to Martens and the others. But it would need to sort out how to run and staff the spots, and it would need boatloads of money for all of it.
This might take a few years. So I stay in the water for as long as I can. I watch a couple more trains cross the bridge. A smiling family glides by in a small boat. Today, the water feels and smells good.
Reluctantly, I haul myself back into the kayak and paddle, ever so slowly, to shore.
Yvonne Abraham is a Globe columnist. Her e-mail is firstname.lastname@example.org.
Correction: Because of a reporting error, a column in Sunday's paper identified the wrong group as organizers of an annual swim race on the Charles River. The race was begun by the Charles River Swimming Club Inc.