I would just like to add to Darth Trom`s post that in the very first level on the yatch you can kill the first 5 guys with stealth kills even on 007 difficulty. These guys are really stupid, well I guess it is a tutorial level. First guy is on the upper deck right when you start. Second guy is in a cabin on a computer at the end of a hallway. Then shoot the fruit bowl on the table to work on another cheeve. Go down the ladder by the table and there will be 3 guys talking. Wait until 2 of them walk away and then it will tell you to hit the X button for a stealth kill as the game puts you in to position to do so. The 4th guy will now be on another computer in the next cabin and the 5th guy must be deaf because he is standing right there watching tv. I would next go up the ladder and kill a 6th guy, run down the hall, trigger a cut scene and a save. Then rinse and repeat. As mentioned by Darth Trom when you come up on someone the X button pops up saying takedown, you have to get a little closer till is says stealth takedown.