This fort can be tricky because of the weather surrounding it. It is often misty/foggy and can be hard to tell how close you are to shore. In addition to the defences, there are also a number of hostile frigates in the nearby area which will move to intercept if you attack the fort. Again it is best to either lure them away and engage them away from the fort, or lure them back through the fort’s attacks to help sink them before focusing on the fort itself.
Dock in the area permitted and follow the path. Climb the rubble between the two burning sections of wall. Drop down and follow the area around to the right to find the first Officer. Kill him and any enemies in the immediate area who trouble you.
Climb the set of stairs close by and turn left at the top. Follow the set path at the base of the wall to the right and you should soon come across the second Officer. Eliminate him and then make your way up the small ramp to the upper level nearby. Take the stairs on the left at the top to find the final Officer. Kill him.
Now that all three Officers have been dealt with, open the door marked with the green objective marker on the central tier of the fort nearby. Kill the enemy inside. This will liberate the fort.