Keep your eyes on the briefcase and follow it from person to person in this espionage mission.
Objective: Track the auction briefcase and watch for hand-offs
Objective: Follow the briefcase unseen
A soon as the man takes the briefcase keep your eyes on it as it's passed from person to person. Go back up the stairs and watch from there, where you get a good view and you won't be spotted.
Objective: Tail the boat carrying the briefcase
Objective: Locate the briefcase unseen
When the briefcase arrives near the pier, get in close and check out the motorbike close by. once the last person moves away, jump on the bike and follow the boat on land.
When the boat arrives remember you need to find the briefcase without being seen. Move the platform and it will rotate to the building. You'll soon see the briefcase and it's now time to get it.
Objective: Infiltrate the marina to get the briefcase
Objective: Escape the marina
Get on to the far left of the platform and swim to the ladder on the left of the garage door. You're now on the north side of the building. You need to head over to the east side of the building where there are three men. Two are stationary and one is patrolling. Get access to the camera to see their locations. Move up the stairs to the main area and wait for the guard on foot to move south. Now move closer to the briefcase and stop near the woodpile and hide until the on-foot guard comes back. You won't make enough noise to alert the guards (unless you start shooting without a silencer). Watch the guards and when they're facing the opposite way head straight for the briefcase.
Once you have the briefcase escape the area the same way you came to complete the mission.