Despite his detailed instructions, Jenifer Clark could not find her boyfriend's townhouse - even though she lived all of 15 minutes away.
"I can get people halfway across the world," she says, "but I have no sense of direction whatsoever."
And they are favored by a group highly motivated to get to their destinations as soon as possible: naked rowers.
Boats caught in those eddies, which can be 60 miles wide, can trap a sailboat or rowboat and consign it to a counterproductive 180-mile circle.
When she first started assembling her charts, she came upon a stunning realization about the raw material.
"It's all free," she says. "I couldn't believe this stuff was free."
The craft used by transatlantic rowers do not resemble the sculls of the Schuykill. They are high-tech vessels equipped with sophisticated communications devices.
She, herself, has come her own circuitous route to the business world, and looking back, she has no regrets about giving up her desk job.
"I make double doing it at home."
She is grateful to her government, and for a current far more confounding to sailors than Ben Franklin could have imagined.