A barge of duck might just mean a floating group of ducks, as barge itself means a floating vessel or plank. It is less likely that the ducks themselves are coming at the boat in a barrage. Respectfully, I personally think that it's more reasonable for the boat to go towards the floating group of ducks, making it seem that the ducks are "oncoming".

'Barrage' not 'barge'. meaning = to direct a concentrated outpouring at something or someone. So if the ducks were coming towards(oncoming) you it would be appropriate to refer to them as a 'barrage of ducks'