You can press cancel, or quit on the bomb, and it just lets you play on with the game without having to need to disarm the bomb.
There are many things you can do during the sinking, and if you get the shawl, and if you don't have one of the items (Vlad has them) you go to the turbine room and he's there. You give him the shawl and he gives you the book, or whatever it is that you don't have and saves himself disguised as a woman.
I usually find it that if I get all the items before the sinking, such as the painting, the necklace and book, and deposit it with the purser and then go and get the notebook. When you get it, Zeitel appears, you let him shoot you and then you swap CDs. The lady then gives you the stuff in your cabin and you go get the note book in Zeitel's cabin C59 I think it is. Disarm the bomb or cancel it, you get the book, and you have all the items at this stage.
Go up the staircase, and emerge on the boat deck on the PORT side. Walk to the aft boat on the PORT side and that talkative couple will appear. They ask you to board the boat with them and if you have all the stuff, just agree to it.
You can also emerge on the starboard side, and walk around and go toward the front on the PORT side again and they will also appear. I don't know how long this happens for, but I don't think it lasts all the way to the end of the game.
Daniel.