In swift water rescue operations we do a very similar thing to set up a quick boat operation. We send a line across the river or stream using a line gun, throw rope or if necessary a swimmer. The line is tensioned and two pulleys are attached with lengths of line or webbing and by adjusting them we can effectively control the boat and position to perform a rescue. Its almost like you're sailing, just using the force of the water on the hull instead of wind on a sail.