He has read the latest findings from the Sixth International Conference on Toxic Cyanobacteria, learning how the Italians, Danes, and Australians combat blooms of the potentially harmful microorganism.
He has consulted with an official from the National Oceanic and Atmospheric Administration, asking about the latest methods for testing for cyanobacteria, large concentrations of which can cause nausea and rashes.
And, he has studied Boston-area rainfall charts, looking for the driest days of the year, when the likelihood of sewers overflowing is lowest.
It is not the typical preparation for a swim race.
But eight months after Frans Lawaetz's first attempt to stage a landmark race in the tea-colored waters of the Charles River was canceled due to a thick bloom of cyanobacteria, he is at it again. Determined to revive a tradition of swimming in the Charles -- for decades unthinkable because of pollution levels -- Lawaetz has culled reports and sifted data to come up with a race date when the water is most likely to be safe.
Yesterday he said that on July 21, he and 62 fellow diehards plan to get into their Speedos, strap on their goggles, and dive in. "Know your enemy, that's the bottom line," Lawaetz said of his approach to race planning.
The racers are coming from all over New England, and many are competitive swimmers like Roberta Allison. The 55-year-old professor at Newbury College swims three times a week in a Boston University pool, has completed an 8-mile race in Boston Harbor, and has raced off Carson Beach in South Boston and Niles Beach in Gloucester. But she has never ventured into the waters of the Charles.
"It's fun to be in a group that's doing something for the first time," she said. "It's a little scary, only from the quality-of-water point of view. But other than that, it's probably easier than swimming in the ocean and certainly a lot warmer. But you've got to believe they would not let you get in if there is any kind of danger."
Environmentalists hope the race will cap a 20-year, $4.5 billion cleanup that aimed to make the river safe for swimming on more than 90 percent of days. Still, determining when the water will be safe requires a tricky bit of forecasting. Last year's race was canceled Sept. 8, just a day before it was to begin, when state officials found that large clumps of cyanobacteria, also known as blue-green algae, had thrived in unusually warm water.
Specialists say that by moving the race date to July, when the water hasn't had as much chance to warm up, organizers have reduced the possibility of health problems.
Yesterday, sitting on a dock near the Hatch Shell, Lawaetz pulled off his socks and dipped his feet into the river, paying no mind to the Duck Boat rumbling past and the Red Line train rolling over the Longfellow Bridge. "It's inviting," said the 28-year-old system analyst who founded the all-volunteer Charles River Swimming Club. "I know it doesn't look like Cancun or anything, but it's fine."
Some Charles River enthusiasts recall that until the 1950s families who wanted to cool off without traveling long distances grabbed towels and headed to the river. On summer days, Magazine Beach in Cambridge looked like Coney Island.
But skeptics abound in a city that inspired the anthem "Dirty Water."
"I'm all for swimming in the ocean, but not the Charles," said Kyle Szary, 27, an American Airlines pilot who was sunning himself and eating cubes of watermelon on a dock by the river yesterday. "It seems to be stagnant, and there's a lot of nasty stuff floating in it."
Lawaetz speaks passionately about the Charles's future. He hopes to have 100 racers. And he foresees a day when people from all over the city will flock to the Charles and swim.
"Imagine on a hot summer's day looking out here and . . . having loads of people splashing around," Lawaetz said, looking out on the river, quiet but for a lone kayaker. "It's unfortunate that's it's not happening now."
Michael Levenson can be reached at email@example.com.