The animated chart on the television screen by the cafeteria is a little disconcerting; according to the flickering arrow, the bow of our ferry will run aground on the north Brittany coast, somewhere around Plouguerneau. Watching for a moment, though, makes it clear that our actual path is a little way off from the ship’s heading, the Captain accurately following an imaginary line that will see us slide past Ushant and south into the Bay of Biscay and, ultimately, to Bilbao.
The discrepancy in our direction is, of course, to compensate for the motion of the wind and water, which have their own ideas about where we should be headed. Navigating on the sea is not like driving along a road. Were the engines to stop, we wouldn’t coast gently to a halt, but instead would be carried who-knows-where by the tides, winds and currents.