There is 3 ship crew mission (icon with 3 small people), they are in New-orléans :Mission 1 : "Mistress and commander"You must beat a man without taking damages for the 100% sync.
My way isn't like in the video, i suggest you to kill all the others enemies (
NOT THE MAIN TARGET) before with your poison dart, for more security.And finish the target with your hands.
Mission 2 : "Before the mast"A mission different from the ordinary this time because it's a race (time trial) against a sailor.For the 100% sync, you've to take no damage.
You have 1 minute to cross 11 checkpoints in a race taking place mainly on roofs, no particular advice, only not to avoid falling, and killing the guard with the pistol, or use a smoke bomb on them to move forward quietly.
Mission 3 : "The cannon"Open the letter : infiltrate discreetly the barracks to steal it the plans of a cannon. To reach there, pass by the covered way, exactly as in a mission of the main story. Collect the contents of the chest and it's finished.Pretty easy.Don't kill the guards for the 100% sync, even just one
I've used the slave suit, cause with her, you can take a box, and you are always hidden, avoid the guards a maximum, up to the chest! There is a wooden box at the entrance of the barracks.
There is 3 videos (
credit to :
AnonymousAffection) below if you want to follow them, especially for the race.