It is simply an absolute fact that the chances are improved at closer range than they are at a farther range. It’s so obvious and clear that no one need to even get into statistics and probability — because everyone knows this inherently...
If you don’t know this inherently, I’m afraid you’re “beyond help” for something like a Free Republic board... :-)
Perhaps I'm beyond help. Perhaps I know the difference between the required accuracy and the actual accuracy of a trained sniper. At 25 meters, they can choose which nostril to put the bullet through although they'd actually aim a bit higher, while at 200 meters there's a little more uncertainty but not enough that the pirate is going to survive long enough to react to being shot. I fired 150 rifle rounds over the weekend (less than usual because I took Easter off), without a single shot that would miss a head at 200 meters, and I would bet that each sniper who took the shot had more practice five days a week than I had Saturday.
As for the moving platform and target, with the reasonably steady rhythm of the waves it's still not a major factor. I'm a lot more worried about the pirates freaking out or panicking over a bird splashing to catch a fish or something natural jumping nearby in the water than I am about an expert missing a critical shot. If I was the hostage, I would have been annoyed that the pirates survived the first 24 hours and angry beyond words that no one dealt with them after they were left alone in the boat during the escape so that it was a clean shot for an amateur with lots of ammunition.