An eight-woman crew cut through the waters of Petaluma River on Sunday and quickly gained on another eight-woman boat.
But just as they charged ahead in near-perfect unison, the other team showed a surge of energy in a noontime heat of the Wine Country Rowing Classic off Shollenberger Park.
For the next 1,500 meters, as soon as one stern lurched forward, the other heaved and pushed ahead, with dueling coxswains urging them on.
"This is called emptying the tank," said chief referee Dave Hayes, 59, of Santa Rosa, who rode behind the teams in a skiff.
"There's something about moving next to somebody," said course marshal Ned Orrett, 63, manning the outboard motor.