As for George Smith, here's another possible scenario:
It is known that occassionally on cruise ships there are small groups of nefarious people on board. Their intent is to rob guests cabins of jewelry, cash, cameras, and other small, easily-transportable items.
As I understand it, (and I'm not making this up!) they will size up potential victims, and when the time is right, slip something into their drinks to knock them out. After that, they take the guest's room key, and rob the cabin. After one or more scores, the pirates get off at the next port of call and vanish.
I think it is possible this is what happened to the Smiths.
Consider this: For a couple who doesn't drink that much, she ends up unconscious, quite far from their cabin. We know this, because it is recorded in the ship's log that security personnel found her there, and in that condition. George is also seen heavily intoxicated, having to be helped to his cabin. Who is it that's helping him to his cabin? And then the loud scuffle inside the cabin -- a robbery attempt gone wrong? So he gets attacked (we know this by the blood found inside the cabin), and pushed overboard?
It's just a possibilty that I have, but it's one that fits the facts.