Many years ago, after a passage up the coast from Norfolk, Virginia, I approached New York Harbor in a real pea-soup fog. As I neared the Verrazano Narrows Bridge, fog horns and the low-pitched throbbing of ship engines seemed to come at me from all sides. I looked off to port as a Plimsoll mark passed by, maybe 50 feet away. I couldn't see the ship it was attached to, just a slight darkening of the fog bank.