A method for processing seismic data acquired using a first over/under streamer and a second over/under streamer. In one implementation, the method may include estimating seismic data that would have been acquired by a third over/under streamer disposed at a depth equivalent to a distance separating the first over/under streamer from the second over/under streamer; and applying a dephase and sum algorithm to seismic data acquired by the first over/under streamer and the second over/under streamer and the estimated seismic data.