When was the last time 15 ocean ships docked almost all at once in New York, and undocked again, and sometimes redocked in-between, all in a week? In the near-400 years since the Dutch first arrived, there have been events even larger. But not many of them lately. Lately, large get-togethers of harbor craft in the most visible parts of the port - upper bay and lower North River - usually surround festive celebrations like the Tug Races and their accompanying games, great entertainment for young and old. But more stirring to watch than tugs at play are tugs at work. Barges go up and down the rivers regularly, but shipdocking, the lively part of tugboating, is concealed from the public eye off the remote corners of Staten Island and the containerports of Newark Bay.