Mark,
There is a difference here. Captain Sullivan's decision to land on the water was the hard part.
The fact that the water was very calm made it easier to land on. Further since it was daytime, that also reduced the problems faced. The bridges and boats also had to be calculated, but most pilots can land on a smooth surface.
Again, it was the decision to do so right away which was hard.
Ten out of ten can make the landing, but before he did it, I would say that only 3 or 4 out of ten would have tried that first. Most would have thought about a landable surface like an airport before looking at a water landing. That time spent could have been the difference.
