Kill the HMS Jersey's Captain
Escape the Jersey without entering open conflict
Swim up to the ship. Head for the pylon you see coming down near the bow of the ship. Climb on up that to the white wooden part. Start on over to the right after that and make your way over in that direction. When you reach the front, climb on up to the top and take out the Soldier that is patrolling the area. This reduces the chances of getting noticed considerably. Take cover at the nearby corner and wait for the Soldier to come to the end and turn away from it.
Head down the stairs and hop over the railing. Quickly move to the next corner and get around it. Once you have, turn and climb on up the windows to the eavesdropping area.