Manny - you confirmed one thing I have written about people who go "missing" at sea - especially young adults. The young man you witnessed jumped while he was still is sight of the pier. In other words, he probably thought he was going to make it ashore.
I can't read minds, but having thought a lot about this topic (as I have to write articles about these things) I have come to the conclusion that some people, most likely strong young adults, jump from the ship thinking they are definitely going to survive.
This is a BIG mistake.
I will admit a couple of things here. When I worked on cruise ships I had that conversation with other staff members. I said I thought I could jump from our ship and survive. They completely disagreed with me, but I remember being very confident in the idea.
Secondly - just a few years ago I was on a very small expedition ship, in Norway, and I was talking to friends. For an inexplicable reason, one guy started the motion to get up and sit atop the railing. He was just absorbed in conversation, and it was there so he went to sit down. It didn't even occur to him for split second that was a bad idea. Of course, we stopped him before he got up there. But he said , "You know, I totally know better, but I just wasn't thinking about that..."
I believe some people do "fall" from cruise ships - but only because they do stupid things like sit on the railing. I personally believe this is how the Connecticut honeymooner case (George Allen Smith) happened. he was alone on his balcony, drunk as a skunk, and he just got up on the railing to smoke a cigarette and fell over. The did find a chair in the corner of the balcony.