Back around 1998 or so Delta Air Lines sponsered a ditching/water survival seminar at it's training center in Atlanta, GA. We invited virtually anyone with an interest in this subject to attend the two day event. The opening speaker was one of Delta's F/O's who had the unfortunente experience of being the co-pilot on a USN, P3 that had ditched south of Petropovlosk back in the early eighties. Of the fourteen crewmembers on board only four or five got out alive and were in turn picked up by the Russian Navy. Actually most of the crew got out, but do to very high seas and extreme wind, they were unable to board rafts and thsu blew away from the resucers. Interestingly the aircraft commander had at one time been a pilot on the USN Marlin flying boats and his skills at getting the P3 on to the water with minimal damage were credited to his previous flying boat experience. As the pilot told the story, you could have heard a pin drop from 100 yards. It was truely spell binding
While I would not take anything away from the USAir crew that landed on the Hudson, there have been several controlled ditchings in the past that far exceed the challenges that this USAir crew experienced. Northwest Airlines ditched a DC7C outside of Manila, at night while on fire after losing a prop which penetrated the cabin, in high seas and only lost one passenger after spending around eight hours afloat in the sea.
Pan American lost two Stratocruisers with minimal loss of life on one, and none on the other. To my knowledge other than a ONA DC9 that ditched in the Carribean after runing out of fuel, there have been no planned ditchings. A few water landings maybe but planned, controlled ditchings I would venture to guess may not have happened....yet.