Zerknijcie tu: http://www.imdb.com/title/tt0470055/board/nest/100234023

"So I was at the bar last night and looked over to my right and recognized the guy sitting next to me. It was none other than world famous Hans Horn, the director of this movie. He sees me gasp in shock and says with a slight grin, "arrrr lemme guess, you wans be knowing de ending?" Although I was confused by his pirate accent, I ignored it and nodded my head. He told me that the friends faked the whole thing to get Amy over her fear of water, knowing that the death of so many friends coupled with the need to save a life would cure this ailment. Apparently there were trained divers underwater swimming the supposed carcasses to safety. The real baby had been silently transported to its grandparents (James' parents obviously, as she murdered her father earlier in her life while they were swimming) while Amy was not drinking alcohol on deck. A replica of the child was created to replace it which explains why she found the baby on the floor (the natural affinity of robots to falling down). The tugboat guy worked for the diving company and was there to clean up (why else would he snoop around someone's yacht right?). The baby he heard was the replica which remained there, and the following scene was Amy on a different yacht they took for a ride after they returned to shore to celebrate her getting over her fear. Hope this helps relieve the mystery behind the movie. On a side note, I got pretty drunk and let's just say that now I know why they call him Hans "The Horn."