Windsurfers often pump their sails back and forth to gain speed, but it can also cause slowing if done incorrectly. The complicated physics of the action was tackled by our group. Recently, the research group examined the propulsive dynamics of sail pumping on sailboards and established two quantities that measure the propulsive performance of pumping sails. The work is published on the reputed fluid dynamics journal Physics of Fluids, and was selected as featured on cover. The AIP Scilight reported the progress https://aip.scitation.org/doi/10.1063/10.0006710.