I stared for a while at the placid face of Long Island Sound before I could make out Bren Smith’s farm. It was a warm, calm morning in September. Sixty buoys bobbed in rows like the capped heads of synchronized swimmers. It wasn’t until Smith cut the engine of his beat-up boat, Mookie, that I knew for sure we had arrived. The farm, a three-acre patch of sea off Stony Creek, Connecticut, starts six feet underwater and descends almost to the ocean floor. From the buoys hang ropes, and from the ropes hang broad, slippery blades of sugar kelp, which have the color and sheen of wet Kodak film.