The passengers and crew were very fortunate that this occurred in New York and the pilot landed in a busy waterway. Suppose this was a flight between Chicago and Detroit and he had to land in Lake Michigan.
There would not have been the ferry boats plying the waters and it might have taken an hour or more to get the necessary rescue boats there. While the Coast Guard would have arrived quickly, their helicopters and small carft would not have been able to handle 150+ people in the short amount of time available.
