Based on the info in this thread, it certainly does seem unlikely that Amy would willingly leave that ship, leave her loving family frantic, and start some new underworld type of life in some foreign land. I also believe that at some point since 1998 (being so high profile), she would have been found or released, or escaped with some sort of help. Most especially if she were traveling such as suggested by the alleged sighting in San Francisco.
Based on this possibilities, I have to once again agree with Otto. I think it's a very high probability that she went over that rail. She was seen on the balconey, had been somewhat seasick the whole trip, and then 20 minutes later she has vanished. She would have definately taken her shoes, at minimum if she were taking off.
Sadly, I believe these sightings are the product of hopeful minds, and of course, that makes sense. I'd think the same things if that were my loved one.
Someone suggested if she had gone overboard she could swim, or would have floated up on some shore. Unlikely. She would have more likely been pulled under the ship...and well...enough said about that. She would have hit the water so hard she would have been knocked out most likely, which is a small bit of a blessing I guess.
All this said, let me take another approach to figuring out this sad mystery. Even though Amy has been described as icon of stability and success, let's for a moment suspend that reality and think how this would have played out if she had been leading a "double life". Outwardly happy, but inwardly struggling.
What happened to her along the way that might have made her "snap" and do something so drastic as take off with a stranger? (Assuming she willingly left). Is there anything in her past or her behavior leading up to that night that would suggest this was even a remote possibility? I'm still not buying the "wholesome girl next door" portrayal. Any female with multiple ear piercings and multiple tattoos back in 1998 was considered "alternative", "edgy", and "wild". And she smoked, which was diametrically opposed to her star athletics. Another odd flag. Something just doesn't add up here, something the general public isn't being told and I guess is none of our business. That said, it's not adding up.
These remarks are not meant disrespectully, or to upset. These remarks are made to help consider all possibilities, and help find this woman and help her get back home to her family. All possibilities should be considered.
Finally, despite the fact the near naked pictures of who is presumed to be Amy must upset her friends and family, they should post them everywhere they can. Near nude pictures draw attention, and people will look at them. It's human nature.
Anything that draws more attention to Amy and her case will get her closer to home.
My heart, and my prayers go to Amy's family, and most especially to her mother. I will continue to pray that they get answers, get closure. Just be sure to consider all possibilities, as difficult as it may be.