SILHOUETTED against a dying sun on a late July evening, more than a dozen Hamptons regulars eased into the warm darkness of Sagaponack Pond.
One by one, they climbed gingerly on top of what looked to be fatter, longer versions of surfboards. They balanced first on their knees, each holding an oar, before rising to stand tall on the boards. Then they quietly paddled off to a beach about a mile away. Gliding past cornfields and multimillion-dollar estates, they shifted their oars from side to side to the rhythm of a drumming circle in the distance. The sky turned lavender.