Imagine if you were part of the Russian mafia or even a speznaz as of the era of FSU and not only were you resentful of perceived hostile foreign powers (Sweden, Estonia, the USA) smuggling out the state secrets of your beloved fatherland and you become aware that this is being done on a public passenger ferry; you have fired off at least two warnings to the western states concerned but it is still going on. So, you have the military and maritime knowhow to take action to put a stop to it. The fact of a thousand members of public and crew are on board is - you reason - something the western powers should have thought about, not your problem - so you move heaven and earth to stop the latest smuggling which you have been tipped off about. So you make darn sure that ship goes nowhere. You wait until it gets into international waters and then on the stroke of Swedish midnight - (Sweden, do you get the message?) - a series of three explosions go off at the bow side locks - did the one at the atlantic lock at the bottom fail? - but you don't know that the car ramp will also come off, do you? So you attach a mine via a mini submarine to the side or accidentally crash the submarine you had tracking the vessel. Job done.