Josh Marshall asks the question:
[H]ere is a list on Wikipedia of survival rates in cases where planes were intentionally ditched or landed in water. The examples run the gamut. But the gist is that while there are a couple cases of 100% survival, those were with planes that were much smaller and carried far fewer people. A Russian passenger plane was ditched in the Neva River in 1963. And everyone survived. But the plane had only a third the number of passengers as yesterday USAir flight had. A plane went down in the water in Java in 2002 after an engine flameout during a hail storm. In that case, one flight attendant died -- out of 66 people aboard the plane.I thought the same thing as Josh. In spite of the "in case of water landing" safety lectures you get when you fly over water, i can't think of a commercial jet that's ever been forced to land in water and done it without casualties.
Most of the ditchings seem to end something like how this one did in 1970 in the caribbean -- with a substantial number of people surviving, but a lot of fatalities too....