These are the thirteenth and fourteenth missions of the game.
During the first part of Barge, you have to help Vesper get across the ship. There will be enemies coming from all around her so make sure you take them all out when you get the chance. After this you have to move through the ship. Remember to use a lot of cover while moving through the ship and watch out for gas tanks that could blow up when shot and kill you.
On Venice, you have to follow Vesper to a trade location. At first you have to follow her and she brings you to a courtyard that you have to clear out. After this, you move through a civilian area and then you have to clear out a dock area. Then you will go to a building where the trade is taking place. The building starts to collapse and you have to keep moving to the top. There are some enemies here and you have to take them out quick so you can keep moving.