When trying to get a line across a wide stream, many attempt dragging the line behin a boat and ferrying straight across.  Seems like it makes sense, the shortest distance between two points is a straight line.  Unfortunately the current drives the boater and rope downstream in a pendulum arc.  We use pendulum arcs all the time when tossing throw ropes from shore to swimmers, works great in that application. 

Lets think about a variation on this method.  Instead of trying to go straight across, start the boat as far upstream as the rope will allow.  Perform the same ferry and the arc will land him on the other side roughly straight across the stream.  This is known as a reverse pendulum.  Just make certain you have more rope than needed to guarantee success - at least 1.5 times the width.