As it happened, there were no survivors.
A few years ago, two helicopters crashed into the East River, within a week of each other. There were no casualties in those two accidents, perhaps because there was no collision involved, but in one of those incidents, a delivery truck driver who saw the helicopter go down dove in and rescued some of the passengers.
What do you think? Is diving in a good idea? I have no idea how deep the Hudson is, and friends who've swam in it for triathlons report that you can't even see your hands in front of you underwater, so I guess it's unlikely you'd be of help, and you could easily be endangering yourself. Reports said that boats on the water tried to come to the rescue, and it's unlikely the boat captains would be on the lookout for a rescue swimmer. You could easily get hit by a speedboat.
Also, the sinking wreckage was releasing air and who knows what else. Eyewitnesses said the water was all churned up above the wreckage after it sank. I suppose that could be dangerous to swim in.
Would you have dove in?
/EDIT: OK, the NYTimes says the wreckage was submerged 30 feet, but I wouldn't have had that information, had I been on the scene.