Limit Regular Kills: 0/15
Kill the Jersey's Captain
Wait in this position. The Captain will make his appearance after a while. The good news is he is marked so you can see is progress around the ship. When he does, hit him with the dart and then wait for the poison to run its course.
With teh captain dead you need to wait for the Soldiers to be distracted. AFter taht just jump off the ship and swim back to shore. There is one more mission to go now.