Ditching of US Airwarys 1549

You might have heard of it in the news, US Airways 1549 ditched (emergency landing on water) in the Hudson River about 6 minutes after takeoff. What happened shortly after takeoff was that the airplane crashed into a group of birds in the air. The birds damaged the engines, therefore the engines cannot "fly" the airplane anymore. It's just like a car without an engine, it cannot move on the road. So, if an airplane cannot fly, what will happen? Fall down immediately, hit the ground and everyone dies? Well, not really. Airplane designers are very clever, they design the plane in such a way that, in case of engine failure, the plane glides down. So there is a chance that the plane can be brought back to earth safely even if the engines do not work anymore.
So, why can this heavy airplane float on water? It's because of the special design of this airplane. There's a device called the "ditch button", when this button is pressed, the airplane closes all its valves and openings so that water cannot go in. That's why the airplane could stay above water and all passengers were safe from being drown.