On the evening of August 8, 1779, soldiers knocked open the sluices of a temporary dam holding back Otsego Lake, the headwaters of the Susquehanna River. At nine o'clock the next morning they paddled and poled over 200 batteaux, heavily laden with provisions, baggage, and munitions, on the now quickened and deeper current of a river that a few days before had lain quiet. The destination of the flotilla and its accompanying foot soldiers was Tioga (Athens, PA) in preparation for a raid into Indian Country. Beyond the building of the dam and the military campaign, examined here is the dam's design, the extent to which the lake's waters were impounded, and, once opened, how effective the discharge was in carrying the batteaux downriver. Was the flood sufficient to float Clinton's batteaux, and can the contemporary reports on downstream effects, some as far away as Athens, be validated?